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51. One-electron pseudopotential calculations of excited states of LiAr, NaAr, and KAr

Author

Fernand Spiegelman, M. B. El Hadj Rhouma, Hamid Berriche, and Zohra Ben Lakhdar

Subjects
Pseudopotential, Argon, Chemistry, Excited state, Ab initio, General Physics and Astronomy, chemistry.chemical_element, Electron, Physical and Theoretical Chemistry, Atomic physics, Valence electron, Diatomic molecule, Ion
Abstract

The potential curves and spectroscopic constants of the excited states of alkali–argon diatomics MRg (M=Li, Na and K, Rg=Ar) are calculated using usual semilocal single valence electron pseudopotentials on alkali atoms [M+]-core pseudopotentials), semilocal pseudopotentials replac(ing all the electrons of argon ([Ar]-core pseudopotentials), and core polarization pseudopotentials on both centers. All states dissociating into Li(2s, 2p, 3s, 3p, 3d, 4s, and 4p), Na(3s, 3p, 3d, 4s, 4p, 4d, 5p) and K(4s, 4p, 5s, 3d, 5p, 4d, 6s, 4f, 6p, 5d, 7s, 5f) are considered. The core–core interactions for Li+Ar and Na+Ar are included using the accurate ab initio potentials of Ahmadi et al. [G. R. Ahmadi, J. Almlof, and I. Roeggen, Chem. Phys. 199, 33 (1995); G. R. Ahmadi and I. Roeggen, J. Phys. B 27, 5603 (1994)] while the K+Ar ion data are determined by MP2 all-electron calculations.

Published
2002

52. STRUCTURE AND ELECTRONIC PROPERTIES OF IONIZED PAH CLUSTERS

Author

Mathias Rapacioli, Damian L. Kokkin, Cyril Falvo, Hassan Sabbah, Antonio Gamboa, Aude Simon, Fernand Spiegelman, Pascal Parneix, Olivier Pirali, Gustavo García, Laurent Nahon, Anthony Bonnamy, Philippe Bréchignac, Léo Dontot, Thomas Pino, and Christine Joblin

Subjects
Chemical physics, Chemistry, Ionization, Structure (category theory), Atomic physics, Electronic properties
Published
2014

53. A density functional tight binding/force field approach to the interaction of molecules with rare gas clusters: Application to (C6H6)+/0Ar n clusters

Author

Aude Simon, Fernand Spiegelman, Christophe Iftner, Mathias Rapacioli, Kseniia Korchagina, Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3)

Subjects
Chemistry, Binding energy, General Physics and Astronomy, Charge density, Electron, Molecular physics, Force field (chemistry), Tight binding, Atom, Physics::Atomic and Molecular Clusters, Molecule, Density functional theory, Physical and Theoretical Chemistry, Atomic physics, Physics::Chemical Physics
Abstract

International audience; We propose in the present paper a SCC-DFTB/FF (Self-Consistent-Charge Density Functional based Tight Binding/Force-Field) scheme adapted to the investigation of molecules trapped in rare gas environments. With respect to usual FF descriptions, the model involves the interaction of quantum electrons in a molecule with rare gas atoms in an anisotropic scheme. It includes polarization and dispersion contributions and can be used for both neutral and charged species. Parameters for this model are determined for hydrocarbon-argon complexes and the model is validated for small hydrocarbons. With the future aim of studying polycyclic aromatic hydrocarbons in Ar matrices, extensive benchmark calculations are performed on (C6H6)+/0Ar n clusters against DFT and CCSD(T) calculations for the smaller sizes, and more generally against other experimental and theoretical data. Results on the structures and energetics (isomer ordering and energy separation, cohesion energy per Ar atom) are presented in detail for n = 1-8, 13, 20, 27, and 30, for both neutrals and cations. We confirm that the clustering of Ar atoms leads to a monotonous decrease of the ionization potential of benzene for n ⩽ 20, in line with previous experimental and FF data.

Published
2014

54. Conformational dynamics and finite-temperature infrared spectra of the water octamer adsorbed on coronene

Author

Fernand Spiegelman, Aude Simon, Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3)

Subjects
010304 chemical physics, Infrared, Chemistry, Analytical chemistry, Infrared spectroscopy, Thermodynamics, 010402 general chemistry, Condensed Matter Physics, 01 natural sciences, Biochemistry, Spectral line, Coronene, 0104 chemical sciences, Molecular dynamics, chemistry.chemical_compound, 0103 physical sciences, Potential energy surface, Physical and Theoretical Chemistry, Conformational isomerism, Isomerization
Abstract

International audience; We present in this work a detailed study of all-atoms conformational dynamics and finite temperature infrared (IR) spectra of the water octamer (H2O)8 adsorbed on coronene (C24H12), a compact Polycyclic Aromatic Hydrocarbon (PAH). The potential energy surface is calculated on-the-fly within the self-consistent-charge density-functional based tight-binding (SCC-DFTB) approach, with modifications insuring the correct description of water-water and water-PAH interactions. On-the-fly Born-Oppenheimer molecular dynamics simulations are performed in the temperature T range 10-300 K starting from the most stable cubic conformer of (H2O)8 adsorbed on C24H12. As T increases, diffusion of (H2O)8 starts, followed by isomerisation processes and "melting" of (H2O)8 for T in the range 150-200 K. These dynamical processes are quantified through the temperature evolution of chosen indicators. We show that the adsorption of (H2O)8 on C24H12 leads to lower isomerisation temperatures than for the bare cluster, in line with an increase of the density of isomers. A comparative analysis of the low-T (harmonic) spectra of bare and adsorbed (H2O)8 is provided. Finally, the evolution of the spectra as a function of T, illustrating the conformational dynamics, is discussed.

Published
2013

55. Automatic Differentiation of the Energy within Self-consistent Tight-Binding Methods

Author

Mathias Rapacioli, Fernand Spiegelman, Antonio Gamboa, Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3)

Subjects
010304 chemical physics, Optimized geometry, Automatic differentiation, Chemistry, Anharmonicity, 02 engineering and technology, Self consistent, 021001 nanoscience & nanotechnology, 01 natural sciences, Computer Science Applications, chemistry.chemical_compound, Tight binding, Acetylene, 0103 physical sciences, Potential energy surface, [CHIM]Chemical Sciences, Physical and Theoretical Chemistry, Atomic physics, Physics::Chemical Physics, 0210 nano-technology, Biological system, Energy (signal processing)
Abstract

International audience; We present and implement the calculation of analytical n-order geometric derivatives of the energy obtained within the framework of the density functional based tight binding approach. The use of automatic differentiation techniques allows a unique implementation for the calculation of derivatives up to any order providing that the computational facilities are sufficient. As first applications, the derivatives are used to build an analytical potential energy surface around the optimized geometry of acetylene. We also discuss the relevant anharmonic contributions that have to be considered when building such an analytical potential energy surface for acetylene, ethylene, ethane, benzene, and naphtalene.

Published
2013

56. Water clusters adsorbed on polycyclic aromatic hydrocarbons: Energetics and conformational dynamics

Author

Aude Simon, Fernand Spiegelman, Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3)

Subjects
010304 chemical physics, Chemistry, Surface Properties, Molecular Conformation, General Physics and Astronomy, Infrared spectroscopy, Water, Molecular Dynamics Simulation, 010402 general chemistry, 01 natural sciences, Coronene, 0104 chemical sciences, Molecular dynamics, chemistry.chemical_compound, 0103 physical sciences, Potential energy surface, Molecule, Physical chemistry, Density functional theory, Polycyclic Compounds, Water cluster, Adsorption, Physical and Theoretical Chemistry, Isomerization
Abstract

International audience; In this work, we present some classical molecular dynamics (MD) simulations and finite temperature infrared (IR) spectra of water clusters adsorbed on coronene (C24H12), a compact polycyclic aromatic hydrocarbon (PAH). The potential energy surface is obtained within the self-consistent-charge density-functional based tight-binding approach with modifications insuring the correct description of water-water and water-PAH interactions. This scheme is benchmarked for the minimal energy structures of (C24H12)(H2O)n (n = 3-10) against density-functional theory (DFT) calculations and for the low-energy isomers of (H2O)6 and (C6H6)(H2O)3 against correlated wavefunction and DFT calculations. A detailed study of the low energy isomers of (C24H12)(H2O)3, 6 complexes is then provided. On-the-fly Born-Oppenheimer MD simulations are performed in the temperature T range 10-350 K for (C24H12)(H2O)n (n = 3-7) complexes. The description of the evolution of the systems with T is provided with emphasis on (C24H12)(H2O)n (n = 3,6). For T in the range 50-150 K, isomerisation processes are observed and when T increases, a solid-to-liquid phase-change like behavior is shown. The desorption of one water molecule is frequently observed at 300 K. The isomerisation processes are evidenced on the finite temperature IR spectra and the results are presented for (C24H12)(H2O)n (n = 3,6). A signature for the edge-coordination of the water cluster on the PAH is also proposed.

Published
2013

57. Absorption spectra of Na atoms in dense He

Author

John F. Kielkopf, Frank Stienkemeier, N. F. Allard, Fernand Spiegelman, Akira Nakayama, Institut d'Astrophysique de Paris (IAP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3)

Subjects
[PHYS]Physics [physics], Materials science, Absorption spectroscopy, Ab initio, chemistry.chemical_element, 01 natural sciences, Atomic and Molecular Physics, and Optics, Spectral line, chemistry, 0103 physical sciences, Atom, Physics::Atomic and Molecular Clusters, Atomic physics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010306 general physics, 010303 astronomy & astrophysics, Quasistatic process, Path integral Monte Carlo, Helium, Line (formation)
Abstract

International audience; We present an analysis of Na-He collisional profiles at high density and very low temperature in a unified line shape semi-classical theory which contains the impact as well the quasistatic limits. Clearly understanding the variation of shape of the two fine-structure components of the 3s−3p line with increasing helium density allows us to understand experimental spectra of a Na atom attached to He nanodroplets. We compare our collisional approach to path integral Monte Carlo calculations using the same ab initio Na-He molecular potentials.

Published
2013

58. Effect of structure and size on the excited states dynamics of CaArn clusters

Author

Jose J. Plata, Fernand Spiegelman, Marie-Catherine Heitz, Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3)

Subjects
Materials science, Argon, 010304 chemical physics, Icosahedral symmetry, Relaxation (NMR), chemistry.chemical_element, Electronic structure, 010402 general chemistry, 01 natural sciences, Atomic and Molecular Physics, and Optics, Spectral line, 0104 chemical sciences, chemistry, Atomic electron transition, Excited state, 0103 physical sciences, Physics::Atomic and Molecular Clusters, Cluster (physics), Atomic physics
Abstract

This article is part of Topical issue: ISSPIC 16 - 16th International Symposium on Small Particles and Inorganic Clusters. Guest editors: Kristiaan Temst, Margriet J. Van Bael, Ewald Janssens, H.-G. Boyen and Françoise Remacle; International audience; The time-resolved photoelectron spectra, probing the non-adiabatic dynamics of CaAr n clusters excited by a pump pulse in the vicinity of the 4s4p 1P line of calcium, are simulated. The simulations involve Diatomics-In-Molecules modelling of the excited electronic structure, excited states dynamics with electronic transitions, and classical approximations to derive the time-resolved photoelectron spectra. The oscillations in the time-dependence of the spectra, associated with the relative motion of calcium with respect to the argon cluster, and the corresponding nonadiabatic relaxation processes are analysed according to cluster size (n ≈ 55 and 147), structure (icosahedral versus cuboctahedral shape) and local environment (substitution versus surface deposition of calcium, surface type).

Published
2013

59. Vibrational spectroscopy and molecular dynamics of water monomers and dimers adsorbed on polycyclic aromatic hydrocarbons

Author

Aude Simon, Joëlle Mascetti, Mathias Rapacioli, Fernand Spiegelman, Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Institut des Sciences Moléculaires (ISM), Université Montesquieu - Bordeaux 4-Université Sciences et Technologies - Bordeaux 1-École Nationale Supérieure de Chimie et de Physique de Bordeaux (ENSCPB)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), and Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure de Chimie et de Physique de Bordeaux (ENSCPB)-Université Sciences et Technologies - Bordeaux 1-Université Montesquieu - Bordeaux 4-Institut de Chimie du CNRS (INC)

Subjects
Water dimer, 010304 chemical physics, Chemistry, Binding energy, General Physics and Astronomy, Infrared spectroscopy, 010402 general chemistry, 01 natural sciences, Coronene, 0104 chemical sciences, chemistry.chemical_compound, Molecular dynamics, Chemical physics, Computational chemistry, 0103 physical sciences, Potential energy surface, Density functional theory, Physical and Theoretical Chemistry, Spectroscopy
Abstract

International audience; This paper reports structures, energetics, dynamics and spectroscopy of H2O and (H2O)2 systems adsorbed on coronene (C24H12), a compact polycyclic aromatic hydrocarbon (PAH). On-the-fly Born-Oppenheimer molecular dynamics simulations are performed for temperatures T varying from 10 to 300 K, on a potential energy surface obtained within the self-consistent-charge density-functional based tight-binding (SCC-DFTB) approach. Anharmonic infrared (IR) spectra are extracted from these simulations. We first benchmark the SCC-DFTB semi-empirical hamiltonian vs. DFT (Density Functional Theory) calculations that include dispersion, on (C6H6)(H2O)1,2 small complexes. We find that charge corrections and inclusion of dispersion contributions in DFTB are necessary to obtain consistent structures, energetics and IR spectra. Using this Hamiltonian, the structures, energetics and IR features of the low-energy isomers of (C24H12)(H2O)1,2 are found to be similar to the DFT ones, with evidence for a stabilizing edge-coordination. The temperature dependence of the motions of H2O and (H2O)2 on the surface of C24H12 is analysed, revealing ultra-fast periodic motion. The water dimer starts diffusing at a higher temperature than the water monomer (150 K vs. 10 K respectively), which appears to be consistent with the binding energies. Qualitative and quantitative analyses of the effects of T on the IR spectra are performed. Anharmonic factors in particular are derived and it is shown that they can be used as signatures for the presence of PAH-water complexes. Finally, this paper lays the foundations for the studies of larger (PAH)m(H2O)n clusters, that can be treated with the efficient computational approach benchmarked in this paper.

Published
2012

60. Perspectives from Quantum Chemistry for molecules and nanograins with astrophysical Interest

Author

Mathias Rapacioli, Aude Simon, and Fernand Spiegelman

Subjects
Chemistry, Computation, Physics, QC1-999, Ab initio, Nanotechnology, Electronic structure, Configuration interaction, 010402 general chemistry, 01 natural sciences, Quantum chemistry, 0104 chemical sciences, Fock space, Coupled cluster, 0103 physical sciences, Statistical physics, 010306 general physics, Wave function
Abstract

Quantum Chemistry methods offer powerful tools for the computation of various properties of molecules and nanoparticles or clusters such as structure, thermodynamics, infrared and electronic spectroscopy, in some cases on a routine basis. However, neither the accuracy nor the applicability of the various methods are uniform, and may depend strongly on the nature and the size of the compounds and the desired properties. The ab initio methods for approaching electronic structure can be classified into two classes. The first class includes wavefunction-based methods, namely post-Hartree Fock schemes in the framework of Configuration Interaction or Coupled Cluster schemes which can now be used for molecules containing up to a few ten atoms (for single geometry calculations) and are likely to provide accurate results whenever applicable. The second class of methods is that of density-based methods which cover systems between a few tens up to a few hundreds of atoms. It is often of broad applicability and satisfactorily accurate in many cases. For more extended systems or extensive calculations, tight-binding type approximations or evolved force-fields (based on bond-orders for instance) are also quite promising. In this overview, we will briefly remind the basics of standard Quantum Chemistry methods and provide a survey of present trends which should be of interest for astrochemistry simulations at the atomic scale.

Published
2012

61. Absorption spectra of NaHe from white dwarfs to helium clusters

Author

Frank Stienkemeier, John F. Kielkopf, Akira Nakayama, Nicole F. Allard, Fernand Spiegelman, Institut d'Astrophysique de Paris (IAP), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3)

Subjects
History, Absorption spectroscopy, Doping, White dwarf, chemistry.chemical_element, Alkali metal, 01 natural sciences, Computer Science Applications, Education, Atmosphere, chemistry, 0103 physical sciences, Cluster (physics), Physics::Atomic and Molecular Clusters, Physics::Atomic Physics, Atomic physics, 010306 general physics, 010303 astronomy & astrophysics, Helium, Line (formation)
Abstract

International audience; The absorption spectrum of Na produced in dense He shows line features, broadening and shift due to extrema in the 3s-3p potential differences of the transitions which contribute to the two fine-structure components. We present here a comprehensive study of NaHe collisional profiles at high density, and temperatures from 5000 K, the temperature prevailing in the atmosphere of ultra-cool white dwarfs, down to 1 K. At extremely low temperatures, experimental measurements and theoretical calculations of helium doped with alkali metals have been the subject of active study. The alkali-metal atoms are weakly bound to helium nanodroplets, and it appears that the dopants are trapped in a shallow dimple on the cluster's surface, rather being solvated inside the cluster.

Published
2012

62. Study of absorption on the wings of sodium resonance line perturbed by molecular hydrogen

Author

Fernand Spiegelman, N. F. Allard, V. A. Alekseev, Institut d'Astrophysique de Paris (IAP), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3)

Subjects
History, Chemistry, Sodium, Brown dwarf, Ab initio, chemistry.chemical_element, 01 natural sciences, Exoplanet, Computer Science Applications, Education, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Atomic physics, 010306 general physics, Absorption (electromagnetic radiation), Unified field theory, 010303 astronomy & astrophysics, Resonance line, Line (formation)
Abstract

International audience; The unified theory line profiles for neutral Na perturbed by H2 are obtained using new set of ab initio potentials calculated for several collision geometries. The results are of interest for modeling exoplanet and brown dwarf atmospheres.

Published
2012

63. Diatomics-in-Molecules Modeling of Many-Body Effects on the Structure and Thermodynamics of Mercury Clusters

Author

Elke Pahl, Peter Schwerdtfeger, Fernand Spiegelman, Florent Calvo, Laboratoire de Spectrométrie Ionique et Moléculaire (LASIM), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3)

Subjects
Physics, Icosahedral symmetry, Thermodynamics, Markov chain Monte Carlo, 02 engineering and technology, 021001 nanoscience & nanotechnology, 01 natural sciences, Diatomic molecule, Computer Science Applications, Maxima and minima, symbols.namesake, 0103 physical sciences, Melting point, symbols, Molecule, Physical and Theoretical Chemistry, van der Waals force, 010306 general physics, 0210 nano-technology, Global optimization
Abstract

International audience; The stable structures and melting behavior of Hgn clusters, 2 ≤ n < 60, have been theoretically investigated using an updated diatomics-in-molecules (DIM) model initially proposed by Kitamura [Chem. Phys. Lett.2006, 425, 2056]. Global optimization and sampling at finite temperature are achieved on the basis of hierarchical and nested Markov chain Monte Carlo methods, respectively. The DIM model predicts highly symmetric icosahedral global minima that are generally similar to the standard van der Waals atomic clusters, without any indication of distorted or low-coordinated geometries, but also at variance with the global minima found with the pairwise Hg2 potential. The combined influences of surface and many-body effects due to s-p mixing are considerable on the melting point: although the model predicts a bulk melting temperature in fair agreement with experimental results, it is found to decrease with increasing cluster size.

Published
2012

64. Collisional line profiles of sodium perturbed by H2 from the optical to the infrared spectral range

Author

John F. Kielkopf, Nicole F. Allard, Giovanna Tinetti, Fernand Spiegelman, J. P. Beaulieu, Institut d'Astrophysique de Paris (IAP), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), University College of London [London] (UCL), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), and Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)

Subjects
Physics, Range (particle radiation), Infrared, Sodium, General Engineering, chemistry.chemical_element, Astronomy and Astrophysics, Astrophysics, 01 natural sciences, Molecular physics, Spectral line, chemistry, Space and Planetary Science, [SDU]Sciences of the Universe [physics], 0103 physical sciences, 010306 general physics, 010303 astronomy & astrophysics, Line (formation)
Abstract

European Conference on Laboratory Astrophysics - ECLA, ECLA, Paris, France.; International audience; Our aim is to present new unified line profiles of sodium perturbed by H2 from the optical to the infrared spectral range. We compare the specific results obtained for the 3s-3p transition to laboratory spectra.

Published
2012

65. Theoretical investigations of the electronic states of NaXe: A comparative study

Author

Jean-Michel Mestdagh, Majdi Hochlaf, F. Ben Salem, M. Ben Bel Haj Rhouma, Fernand Spiegelman, Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées, Laboratoire Francis PERRIN (LFP - URA 2453), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Modélisation et Simulation Multi Echelle (MSME), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Université Paris-Est Marne-la-Vallée (UPEM), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Université Paris-Est Marne-la-Vallée (UPEM)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), and Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)

Subjects
Valence (chemistry), 010304 chemical physics, Chemistry, Ab initio, General Physics and Astronomy, 010402 general chemistry, 01 natural sciences, Electron electric dipole moment, Molecular physics, 0104 chemical sciences, Pseudopotential, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, Condensed Matter::Materials Science, symbols.namesake, Dipole, Ab initio quantum chemistry methods, Excited state, 0103 physical sciences, Physics::Atomic and Molecular Clusters, Rydberg formula, symbols, Physical and Theoretical Chemistry, Atomic physics, ComputingMilieux_MISCELLANEOUS
Abstract

The electronic state properties of NaXe are investigated using ab initio methodologies and various pseudopotential approaches for comparison. The spectroscopic terms and dipole moments of the lowest electronic states up to the Na(3d) +Xe dissociation limit are determined. The difference between valence or smaller core pseudopotential on Xe is shown to be negligible and so is the difference between all-electron and valence pseudopotential completed by core-polarization treatments of Na. These calculations are used as references to test the performance of a treatment involving a zero electron pseudopotential description of xenon together with a one-electron pseudopotential description of Na. When compared with the reference calculations, the one-electron model leads to reasonable quantitative results. The potential energy curves and spectroscopic data of all Rydberg excited states of NaXe up the Na(5f)+Xe dissociation limit are determined using this method. Long distance wells and barriers in the range R = 15-40 bohrs are identified for some of the higher states with (2)Σ(+) symmetry.

Published
2012

66. PAH-related Very Small Grains in photodissociation regions: implications from molecular simulations

Author

Baptiste Joalland, Mathias Rapacioli, André Mirtschink, Olivier Berné, Aude Simon, Dahbia Talbi, Christine Joblin, J. Montillaud, Fernand Spiegelman, Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Centre d'étude spatiale des rayonnements (CESR), Observatoire Midi-Pyrénées (OMP), Météo-France -Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-Météo-France -Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées, Laboratoire Univers et Particules de Montpellier (LUPM), Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), and Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2)

Subjects
Physics, education.field_of_study, Molecular cloud, Monte Carlo method, Population, Binding energy, Photodissociation, General Engineering, Nucleation, Astronomy and Astrophysics, 01 natural sciences, Quantum chemistry, Molecular dynamics, Space and Planetary Science, Chemical physics, 0103 physical sciences, [PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph], Atomic physics, 010306 general physics, education, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

International audience; The analysis of mid-IR emission suggests that a population of PAH-related very small grains containing a few hundreds of atoms are present in the deep regions of molecular clouds, although no specific species has been identified yet. In this review, we discuss several candidates for these grains: neutral and ionised PAH clusters and complexes of PAHs with Si atoms. The theoretical modelling of the properties of such molecular complexes or nanograins is a challenging task. We first present an overview of quantum chemistry derived models which can be efficiently used on-the-fly in extensive sampling of the potential energy surfaces, as required by structural optimization, classical molecular dynamics or Monte Carlo algorithms. From the simulations, various observables can be determined, such as the binding energies, finite temperature IR spectra, nucleation and evaporation rates. We discuss the relevance of those candidates in the molecular clouds photodissociation regions and propose constrains and perspectives for the nature and size of those very small grains.

Published
2011

67. [FePAH]+ complexes and [FexPAHy]+ clusters in the interstellar medium: stability and spectroscopy

Author

Christine Joblin, Mathias Rapacioli, Fernand Spiegelman, Aude Simon, Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Univ Toulouse UPS, Ctr Etud Spatiale Rayonnements, F-31062 Toulouse 9, France, Centre Etud Spatiale Rayonnements Toulouse, Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)

Subjects
Physics, 010504 meteorology & atmospheric sciences, Photodissociation, General Engineering, Infrared spectroscopy, Astronomy and Astrophysics, 7. Clean energy, 01 natural sciences, Stability (probability), Interstellar medium, Space and Planetary Science, 0103 physical sciences, Theoretical methods, High spatial resolution, Physical chemistry, [PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph], Atomic physics, Spectroscopy, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Line (formation)
Abstract

International audience; The relevance of organometallic complexes in the chemistry of the interstellar medium (ISM) was first suggested in the early 90s. This initial proposal has recently been re-considered in the light of new astronomical data, benefiting from pioneering experimental techniques and theoretical methods. In this article, a review of recent theoretical and experimental results obtained for PAHs coordinated to Fe atoms is presented, focusing on: -(i)- the IR spectra of [FePAH]+ and [Fe(PAH)2]+ complexes, found to be in line with the AIBs, with additional specific features in the far-IR range and -(ii)- the photo-evaporation of [FexPAHy]+ clusters as possible candidates for very small grains releasing PAHs in photodissociation regions. These results call for new astronomical data at high spatial resolution. Studies on larger clusters will require further experimental and theoretical developments.

Published
2011

68. Molecular dynamics simulations on [FePAH]+ π-complexes of astrophysical interest: anharmonic infrared spectroscopy

Author

Mathias Rapacioli, Fernand Spiegelman, Mathieu Lanza, Aude Simon, Baptiste Joalland, Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Centre d'étude spatiale des rayonnements (CESR), Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées, Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), and Météo-France -Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-Météo-France -Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3)

Subjects
010304 chemical physics, Chemistry, Anharmonicity, General Physics and Astronomy, Charge density, Infrared spectroscopy, 01 natural sciences, Molecular physics, Spectral line, Coronene, Molecular dynamics, Microcanonical ensemble, chemistry.chemical_compound, 0103 physical sciences, Potential energy surface, Physical chemistry, Physical and Theoretical Chemistry, [CHIM.OTHE]Chemical Sciences/Other, 010303 astronomy & astrophysics
Abstract

International audience; In this article, classical Born-Oppenheimer molecular dynamics (MD) simulations in the microcanonical ensemble are performed on neutral and cationic polycyclic aromatic hydrocarbon (PAH) species, focusing on [FePAH](+)π-complexes. Their anharmonic mid-infrared (mid-IR) spectra in the classical approximation are derived. This approach allows us to describe the influence of the energy of a system on its IR spectrum in terms of band-shifts and broadenings. The MD simulations are performed on a potential energy surface (PES) described at the self-consistent-charge density functional tight-binding level of theory. The PES is benchmarked on DFT calculations, showing the validity of the approach for complexes of Fe(+) with PAHs larger than coronene (C(24)H(12)) that are of astrophysical interest. MD simulations at high temperature show the occurrence of the diffusion of the Fe cation on the surface of the PAH. It proceeds through the edge of the carbon skeleton which is the lowest energy pathway presenting barriers smaller than 1 eV. Although only qualitative information on the band broadenings can be obtained, we show that the dependence of the computed positions of the main bands of [C(24)H(12)](0/+)and [FeC(24)H(12)](+)π-complexes on temperature can be fit by linear laws. The spectral trends determined for [FeC(24)H(12)](+) are compared to those of N-substituted [C(23)NH(12)](+)and [SiC(24)H(12)](+)π-complexes of astrophysical interest.

Published
2011

69. Modeling Charge Resonance in Cationic Molecular Clusters: Combining DFT-Tight Binding with Configuration Interaction

Author

Fernand Spiegelman, Anthony Scemama, André Mirtschink, Mathias Rapacioli, Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC), Groupe Méthodes et outils de la chimie quantique (LCPQ) (GMO), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)

Subjects
Water dimer, Valence (chemistry), 010304 chemical physics, Dimer, Binding energy, Configuration interaction, 010402 general chemistry, 01 natural sciences, Molecular physics, Dissociation (chemistry), 0104 chemical sciences, Computer Science Applications, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, chemistry.chemical_compound, Tight binding, chemistry, 0103 physical sciences, Potential energy surface, Physics::Atomic and Molecular Clusters, Physical and Theoretical Chemistry, Atomic physics, Physics::Chemical Physics
Abstract

International audience; In order to investigate charge resonance situations in molecular complexes, Wu et al. (J. Chem. Phys. 2007, 127, 164119) recently proposed a configuration interaction method with a valence bond-like multiconfigurational basis obtained from constrained DFT calculations. We adapt this method to the Self-Consistent Charge Density-Functional-based Tight Binding (SCC-DFTB) approach and provide expressions for the gradients of the energy with respect to the nuclear coordinates. It is shown that the method corrects the wrong SCC-DFTB behavior of the potential energy surface in the dissociation regions. This scheme is applied to determine the structural and stability properties of positively charged molecular dimers with full structural optimization, namely, the benzene dimer cation and the water dimer cation. The method yields binding energies in good agreement with experimental data and high-level reference calculations.

Published
2011

70. Molecular dynamics simulations of anharmonic infrared spectra of [SiPAH](+) pi-complexes

Author

Aude Simon, Fernand Spiegelman, Mathias Rapacioli, Baptiste Joalland, Colin J. Marsden, Christine Joblin, Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Centre d'étude spatiale des rayonnements (CESR), Observatoire Midi-Pyrénées (OMP), Météo-France -Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-Météo-France -Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées, Chimie des éléments d & f (LCPQ), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), and Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3)

Subjects
010304 chemical physics, Anharmonicity, Analytical chemistry, Charge density, Infrared spectroscopy, 02 engineering and technology, Ovalene, 021001 nanoscience & nanotechnology, 01 natural sciences, Potential energy, Molecular physics, Interstellar medium, chemistry.chemical_compound, Molecular dynamics, Tight binding, chemistry, 0103 physical sciences, Physical and Theoretical Chemistry, Physics::Chemical Physics, 0210 nano-technology, Astrophysics::Galaxy Astrophysics
Abstract

International audience; This paper presents an investigation of anharmonic effects in the IR spectra of [SiPAH]+ complexes by using Born−Oppenheimer molecular dynamics for a variety of PAHs ranging from naphthalene (C10H8) to ovalene (C32H14). The potential energy surfaces are calculated with the self-consistent charge density functional-based tight binding approach (DFTB). The DFTB parameters are modified to reproduce potential energy surfaces and the harmonic infrared spectra of the studied complexes with respect to DFT calculations. For bare PAHs, we find that the evolution of the vibrational frequencies of the C−H out-of-plane bending and C−C stretching modes as a function of temperature follows a linear law in quantitative agreement with experimental data. For cationic PAHs, the anharmonicity of the bands in terms of position shifts is found to be enhanced with respect to that of neutrals. As compared with bare cationic PAHs, the coordination of Si induces (i) larger broadenings, (ii) a slightly larger shift of the C−C stretching mode, and (iii) a smaller shift of the C−H out-of-plane bending modes. We discuss the implications of the work and the spectroscopic constraints for the detection of [SiPAH]+ in the interstellar medium.

Published
2010

71. Relaxation dynamics of photoexcited calcium deposited on argon clusters: theoretical simulation of time-resolved photoelectron spectra

Author

Laurent Teixidor, Fernand Spiegelman, Nguyen-Thi Van-Oanh, Marie-Catherine Heitz, Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Laboratoire de Photophysique Moléculaire (PPM), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11), Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3)

Subjects
Argon, 010304 chemical physics, Chemistry, chemistry.chemical_element, Chromophore, 010402 general chemistry, 01 natural sciences, 0104 chemical sciences, Photoexcitation, 13. Climate action, Ab initio quantum chemistry methods, Atomic electron transition, Excited state, 0103 physical sciences, Vibrational energy relaxation, Physics::Atomic and Molecular Clusters, Relaxation (physics), Physical and Theoretical Chemistry, Atomic physics, Physics::Chemical Physics, [CHIM.OTHE]Chemical Sciences/Other
Abstract

International audience; Relaxation dynamics following photoexcitation of a calcium atom deposited on an icosahedral-like argon cluster Ar(n) (n approximately = 55) is investigated through theoretical simulations. Based on ab initio calculations of the CaAr molecule, a diatomics-in-molecules model is set up to efficiently describe the electronic excited states of the system. The excited state dynamics is studied using molecular dynamics with electronic transitions (Tully, J. C. J. Chem. Phys. 1990, 93, 1061). The signature of this dynamics in the time-resolved photoelectron spectra is investigated, to assess the possibility of detecting competing vibrational and electronic relaxations through pump-probe experiments. The vibrational relaxation, influenced by nonadiabatic transitions, can clearly be seen in the time-resolved photoelectron spectra. The details of the electronic relaxation, as well as the possible ejection of the chromophore, are found to be sensitive to the local environment of the calcium atom deposited on the argon cluster.

Published
2010

72. Dynamics of highly excited barium atoms deposited on large argon clusters. I. General trends

Author

Benoît Soep, Jean-Michel Mestdagh, Lionel Poisson, Fernand Spiegelman, Marc-André Gaveau, Vincent Mazet, A. Masson, Laboratoire Francis PERRIN (LFP - URA 2453), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Sciences de l'Image, de l'Informatique et de la Télédétection, équipe MIV (LSIIT / MIV), Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), and Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)

Subjects
General Physics and Astronomy, chemistry.chemical_element, barium, photoionisation, 7. Clean energy, 01 natural sciences, photoelectron spectra, Ionization, 0103 physical sciences, Cluster (physics), Astrophysics::Solar and Stellar Astrophysics, Physical and Theoretical Chemistry, 010306 general physics, excited states, Argon, 010304 chemical physics, Relaxation (NMR), Barium, Photoelectric effect, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, molecular clusters, chemistry, Excited state, Femtosecond, argon, 36.40.Cg Electronic and magnetic properties of clusters - 36.40.Mr Spectroscopy and geometrical structure of clusters - 33.80.Eh Autoionization, photoionization, and photodetachment - 33.80.Rv Multiphoton ionization and excitation to highly excite, molecule-photon collisions, Atomic physics
Abstract

33.60.+q Photoelectron spectra; International audience; Ba(Ar) ≈ 750 clusters were generated by associating the supersonic expansion and the pick-up techniques. A femtosecond pump (266.3 nm)-probe (792 or 399.2 nm) experiment was performed to document the dynamics of electronically excited barium within the very multidimensional environment of the argon cluster. Barium was excited in the vicinity of the 6s9p 1P state and probed by ionization. The velocity imaging technique was used to monitor the energy distribution of photoelectrons and photoions as a function of the delay time between the pump and the probe pulses. A complex dynamics was revealed, which can be interpreted as a sequence/superposition of elementary processes, one of which is the ejection of barium out of the cluster. The latter has an efficiency, which starts increasing 5 ps after the pump pulse, the largest ejection probability being at 10 ps. The ejection process lasts at a very long time, up to 60 ps. A competing process is the partial solvation of barium in low lying electronic states. Both processes are preceded by a complex electronic relaxation, which is not fully unraveled here, the present paper being the first one in a series.

Published
2010

73. Correction for dispersion and coulombic interactions in molecular clusters with density-functional derived methods : Application to polycyclic aromatic hydrocarbon

Author

Gotthard Seifert, Fernand Spiegelman, Mathias Rapacioli, Dahbia Talbi, Annick Goursot, Tzonka Mineva, Thomas Heine, Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC), Groupe de Recherche en Astronomie et Astrophysique du Languedoc (GRAAL), Université Montpellier 2 - Sciences et Techniques (UM2)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC), School of Engineering and Science [Bremen] (JU-SES), Jacobs University [Bremen], Physikalische Chemie, TU Bremen, Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), and Institut de Chimie du CNRS (INC)-Université Montpellier 2 - Sciences et Techniques (UM2)-Université Montpellier 1 (UM1)-Centre National de la Recherche Scientifique (CNRS)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)

Subjects
010304 chemical physics, Chemistry, General Physics and Astronomy, Charge (physics), 010402 general chemistry, 01 natural sciences, Molecular physics, London dispersion force, Coronene, 0104 chemical sciences, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, symbols.namesake, chemistry.chemical_compound, Tight binding, 0103 physical sciences, symbols, Physics::Atomic and Molecular Clusters, Nuclear force, Density functional theory, Physical and Theoretical Chemistry, van der Waals force, Atomic physics, Physics::Chemical Physics, Mulliken population analysis
Abstract

International audience; The density functional based tight binding (DFTB) is a semiempirical method derived from the density functional theory (DFT). It inherits therefore its problems in treating van der Waals clusters. A major error comes from dispersion forces, which are poorly described by commonly used DFT functionals, but which can be accounted for by an a posteriori treatment DFT-D. This correction is used for DFTB. The self-consistent charge (SCC) DFTB is built on Mulliken charges which are known to give a poor representation of Coulombic intermolecular potential. We propose to calculate this potential using the class IV/charge model 3 definition of atomic charges. The self-consistent calculation of these charges is introduced in the SCC procedure and corresponding nuclear forces are derived. Benzene dimer is then studied as a benchmark system with this corrected DFTB (c-DFTB-D) method, but also, for comparison, with the DFT-D. Both methods give similar results and are in agreement with references calculations (CCSD(T) and symmetry adapted perturbation theory) calculations. As a first application, pyrene dimer is studied with the c-DFTB-D and DFT-D methods. For coronene clusters, only the c-DFTB-D approach is used, which finds the sandwich configurations to be more stable than the T-shaped ones.

Published
2009

74. Modelling singly ionized coronene clusters

Author

Mathias Rapacioli, Fernand Spiegelman, Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse)

Subjects
Physics, 010304 chemical physics, Binding energy, Optical physics, Configuration interaction, 010402 general chemistry, 01 natural sciences, Bond-dissociation energy, Atomic and Molecular Physics, and Optics, Coronene, 0104 chemical sciences, Delocalized electron, chemistry.chemical_compound, chemistry, Ionization, 0103 physical sciences, Physics::Atomic and Molecular Clusters, Ionization energy, Atomic physics
Abstract

International audience; We introduce a model combining a density functional based tight-binding method with a configuration interaction like scheme to treat charge delocalization in ionized molecular clusters. As an application, we determine the size-evolution of some properties of stack coronene clusters, namely charge delocalization, binding energies and ionization potentials.

Published
2009

75. Evidence for a non-Rydberg molecular doubly excited state of Ca2

Author

Marc-André Gaveau, Thomas Bouissou, G. Durand, Marie-Catherine Heitz, J. M. Mestdagh, Fernand Spiegelman, Laboratoire Francis PERRIN (LFP - URA 2453), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse)

Subjects
010304 chemical physics, Chemistry, Avoided crossing, Ab initio, General Physics and Astronomy, 01 natural sciences, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, Dipole, symbols.namesake, Excited state, 0103 physical sciences, Rydberg formula, symbols, Molecular orbital, Physical and Theoretical Chemistry, Atomic physics, 010306 general physics, Adiabatic process, Excitation
Abstract

We report experimental and theoretical evidence of a non-Rydberg molecular doubly excited state of Ca 2 involving excited molecular orbitals mixing 4p and 3d characters. The excitation spectrum of Ca 2 , carried by helium or argon clusters, is recorded experimentally in the range 25 600–27 800 cm −1 , displaying a bimodal structure. The latter is interpreted from ab initio calculation and analysis of the adiabatic states of Ca 2 up to doubly excited asymptotes Ca(4p3d 1 D) + Ca(4s 2 1 S) and Ca(4s3d 3 D) + Ca(4s4p 3 P), and the relevant dipole transition moments. The bimodal structure is assigned as resulting from the avoided crossing between adiabatic states 3 1 Π u and 4 1 Π u , reflecting the mixing of doubly excited configurations and absorbing singly excited configurations.

Published
2009

76. Effect of an ionic impurity on the caloric curves of water clusters

Author

J. Douady, Florent Calvo, Fernand Spiegelman, Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Laboratoire de Spectrométrie Ionique et Moléculaire (LASIM), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3)

Subjects
Materials science, 010304 chemical physics, Hydronium, Triatomic molecule, Monte Carlo method, Thermodynamics, 02 engineering and technology, PACS: 36.40.Ei Phase transitions in clusters - 65.20.Jk Studies of thermodynamic properties of specific liquids - 61.20.Ja Computer simulation of liquid structure, 021001 nanoscience & nanotechnology, 01 natural sciences, Heat capacity, Atomic and Molecular Physics, and Optics, chemistry.chemical_compound, chemistry, Impurity, 0103 physical sciences, Melting point, Molecule, Physical chemistry, Water cluster, [PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph], 0210 nano-technology
Abstract

International audience; The equilibrium heat capacities of model pure and heterogeneous water clusters have been calculated using exchange Monte Carlo simulations. For the pure water cluster (H2O)20, microcanonical and canonical caloric curves obtained from various rigid intermolecular potentials indicate the onset of melting to lie in the range 140-180 K, in reasonable agreement with previous estimates. Clusters doped with a single hydronium or ammonium impurity show a significant shift of the melting point in the 20-molecule system, but a reduced effect when 50 molecules are reached.

Published
2009

77. Ab-initio calculation of the ground and excited states of MgH using a pseudopotential approach

Author

Benoît Soep, P. de Pujo, J. M. Mestdagh, Fernand Spiegelman, Laboratoire Francis PERRIN (LFP - URA 2453), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)

Subjects
MAGNESIUM DEUTERIDE, POLARIZATION, Ab initio, General Physics and Astronomy, Electronic structure, 010402 general chemistry, 01 natural sciences, Pseudopotential, CONFIGURATION-INTERACTION, 0103 physical sciences, X-2-SIGMA(+), Physical and Theoretical Chemistry, MOLECULE, Spectroscopy, 010304 chemical physics, Chemistry, Operator (physics), CAH, CONSTANTS, Configuration interaction, Potential energy, 3. Good health, 0104 chemical sciences, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, LYING ELECTRONIC STATES, Excited state, EMISSION-SPECTRA, Atomic physics, SYSTEM
Abstract

The electronic structure of the MgH molecule is investigated using a pseudopotential description of the Mg 2 + core, complemented by a core polarization operator. The electronic problem is treated by the Internally Contracted Multi-Reference Configuration Interaction method (IC-MRCI). The potential energy curves and the molecular constants are calculated for all MgH molecular states dissociating up to the excited atomic configurations Mg(3s3d1D) + H(1s2S). A good agreement with the available experimental data is found. These calculations help to clarify the very complicated spectroscopy of MgH in the 35 000–46 000 cm - 1 excitation range, where many states correlated with the 3s3p, 3s4s and 3s3d atomic configurations cross one another. For instance, the predissociation mechanism of the B 2 Σ + state is enlighten. Both the doublet and quartet systems are documented.

Published
2009

78. Structure, stability, and infrared spectroscopy of (H(2)O)(n)NH(4)(+) clusters: A theoretical study at zero and finite temperature

Author

Fernand Spiegelman, Julie Douady, Florent Calvo, Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Laboratoire de Spectrométrie Ionique et Moléculaire (LASIM), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3)

Subjects
Surface Properties, Monte Carlo method, General Physics and Astronomy, Electronic structure, 010402 general chemistry, Vibration, 01 natural sciences, Motion, Polarizability, 0103 physical sciences, Molecule, Physics::Chemical Physics, Physical and Theoretical Chemistry, Basis set, ComputingMilieux_MISCELLANEOUS, 010304 chemical physics, Chemistry, Spectrum Analysis, Temperature, Water, 0104 chemical sciences, Hybrid functional, Quaternary Ammonium Compounds, Chemical physics, Molecular vibration, Quantum Theory, Thermodynamics, Density functional theory, Atomic physics, Monte Carlo Method
Abstract

The combined effects of size and temperature on the stable structures of water clusters doped with one ammonium molecule have been investigated theoretically using an empirical potential and density-functional theory (DFT) calculations. Global optimization with Monte Carlo methods has been performed using an explicit intermolecular potential based on the Kozack-Jordan polarizable model. Putative lowest-energy structures based on this empirical potential are reported. Our results indicate a high propensity for the NH(4)(+) impurity to be fully solvated by water molecules. Clathratelike patterns are formed for clusters containing more than 11 molecules. Local reoptimizations of candidate structures carried out at the DFT level with the B3LYP hybrid functional and the 6-311++G(d,p) basis set confirm the general trends obtained with the intermolecular potential. However, some reorderings between isomers often due to zero-point energy corrections are found in small clusters, leading to stable geometries in agreement with other first-principles studies. Temperature effects have been assessed using a simple harmonic superposition approximation for selected cluster sizes and using dedicated Monte Carlo simulations for (H(2)O)(20)NH(4)(+). The clusters are found to melt near 200 K, and possibly isomerize already below 50 K. The free energy barrier for core/surface isomerization of the impurity in the 21-molecule cluster is estimated to be only a few kcal/mol at 150 K. The vibrational spectroscopic signatures of the clusters obtained from the electronic structure calculations show the usual four O-H stretching bands. As the cluster size increases, the double acceptor-single donor band near 3700 cm(-1) increasingly dominates over the three other bands. While we do not find conclusive evidence for a O-H stretching spectroscopic signature of the ammonium impurity to be in the core or at the surface in the 20-molecule cluster, a possible signature via the N-H stretching bands is suggested near 2800-2900 cm(-1). In the larger (H(2)O)(49)NH(4)(+) cluster, the impurity is slightly more stable at the surface.

Published
2008

79. Influence of electronic excitations on the thermodynamics of small carbon clusters: the example of C-3(+)

Author

Laurent Montagnon, Fernand Spiegelman, Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse)

Subjects
Physics, Monte Carlo method, Degrees of freedom (physics and chemistry), Optical physics, chemistry.chemical_element, Electron, 010402 general chemistry, 01 natural sciences, 7. Clean energy, Atomic and Molecular Physics, and Optics, 0104 chemical sciences, Ion, Thermalisation, chemistry, Excited state, 0103 physical sciences, Atomic physics, 010306 general physics, Carbon
Abstract

We illustrate the influence of the thermalization of electrons on the linear-cyclic isomerization of small carbon clusters by model Monte Carlo calculations of C3 + at 3500 K. It is shown that the inclusion of the electronic degrees of freedom, in such systems with several low-lying excited states, can significantly change the relative isomer populations and energy distributions, as compared with equivalent electronic ground-state simulations.

Published
2007

80. Fragmentation induced by charge exchange in collisions of charged alkaline clusters with alkali atoms

Author

B. Zarour, Marie-Françoise Politis, Sergio Díaz-Tendero, Fernand Spiegelman, J. Hanssen, Florent Calvo, L. F. Ruiz, Fernando Martín, Paul-Antoine Hervieux, Institut de minéralogie et de physique des milieux condensés (IMPMC), Université Pierre et Marie Curie - Paris 6 (UPMC)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Departamento de Química, C-9, Universidad Autónoma de Madrid, Universidad Autonoma de Madrid (UAM), Laboratoire de physique moléculaire et des collisions (LPMC), Université Paul Verlaine - Metz (UPVM), Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), Université Louis Pasteur - Strasbourg I-Centre National de la Recherche Scientifique (CNRS), Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris Diderot - Paris 7 (UPD7)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS), Universidad Autónoma de Madrid (UAM), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)

Subjects
Physics, Branching fraction, Aucun, Optical physics, 02 engineering and technology, PACS : 34.70.+e Charge transfer - 36.40.Qv Stability and fragmentation of clusters - 36.40.Wa Charged clusters, 021001 nanoscience & nanotechnology, 01 natural sciences, Heat capacity, Atomic and Molecular Physics, and Optics, Ion, symbols.namesake, Fragmentation (mass spectrometry), [PHYS.COND.CM-GEN]Physics [physics]/Condensed Matter [cond-mat]/Other [cond-mat.other], 0103 physical sciences, Density of states, Cluster (physics), symbols, Physics::Atomic and Molecular Clusters, Physics::Atomic Physics, Atomic physics, 010306 general physics, 0210 nano-technology, Hamiltonian (quantum mechanics)
Abstract

We present a theoretical study of the dissociative charge transfer processes induced by collisions between doubly-charged alkaline clusters and alkaline atoms at slow and intermediate impact energies. Charge-exchange cross sections have been evaluated for the collisions of Li31 2+ and Na31 2+ clusters with neutral alkaline atoms (Cs and Na) at impact energies between 500 and 4000 eV. The branching ratios of the evaporation processes have been calculated within the framework of the microcanonical statistical theory of Weisskopf. The key ingredient of this model is the cluster vibrational density of states. An approach based on quantum tight-binding Hamiltonian is introduced, allowing us to evaluate this quantity at a microscopic level, including quantum vibrational effects at low temperatures. Comparison with previously reported results obtained using a macroscopic description of the level density are presented and discussed.

Published
2007

81. Quantum Effects on the Caloric Curves of Lithium Clusters

Author

Fernand Spiegelman, Florent Calvo, Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3)

Subjects
010304 chemical physics, Chemistry, Monte Carlo method, General Chemistry, 01 natural sciences, Heat capacity, Premelting, symbols.namesake, Tight binding, 0103 physical sciences, symbols, Statistical physics, Configuration space, 010306 general physics, Hamiltonian (quantum mechanics), Quantum, ComputingMilieux_MISCELLANEOUS, Embedded atom model
Abstract

A tight-binding quantum Hamiltonian and an empirical embedded-atom model (EAM) potential are used to get insight into the finite-temperature behavior of small Lin clusters, n = 8, 20, and 55. Exchange Monte Carlo simulations provide an extensive sampling of configuration space, including the putative global minimum and many relevant isomers. The heat capacities obtained from the classical simulations are corrected for low-temperature quantum delocalization using the Pitzer-Gwinn approximation. Alternatively, the caloric curves are estimated from the database of local minima using the quantum harmonic superposition approximation. While the two atomistic models predict qualitatively similar features, including some premelting effects in Li20 but none in Li55, strong variations are observed in the melting temperatures, the EAM potential giving unexpectedly low values.

Published
2007

82. Electric dipoles and susceptibilities of alkali clusters/fullerene complexes: Experiments and simulations

Author

Driss Rayane, Florent Calvo, Michel Broyer, Isabelle Compagnon, Fernand Spiegelman, Franck Rabilloud, Rodolphe Antoine, Philippe Dugourd, Laboratoire de Spectrométrie Ionique et Moléculaire (LASIM), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)

Subjects
Fullerene, Chemistry, 02 engineering and technology, 021001 nanoscience & nanotechnology, Alkali metal, 01 natural sciences, 3. Good health, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials, Electric dipole moment, General Energy, Computational chemistry, Chemical physics, 0103 physical sciences, Molecule, Physical and Theoretical Chemistry, 010306 general physics, 0210 nano-technology, ComputingMilieux_MISCELLANEOUS
Abstract

Using a combination of deflection experiments and atomistic modeling, we investigate the structural and electrostatic properties of lithium and sodium clusters on a C60 molecule. The electric susce...

Published
2007

83. Formation and destruction of polycyclic aromatic hydrocarbon clusters in the interstellar medium

Author

Fernand Spiegelman, Pascal Parneix, D. Toublanc, C. Joblin, Florent Calvo, and Mathias Rapacioli

Subjects
Physics, Infrared, Astrophysics (astro-ph), Time evolution, Nucleation, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Photodissociation region, Coronene, Interstellar medium, chemistry.chemical_compound, chemistry, Space and Planetary Science, Chemical physics, Atomic model, Cluster (physics), Physics - Atomic and Molecular Clusters, Atomic and Molecular Clusters (physics.atm-clus), Astrophysics::Galaxy Astrophysics
Abstract

The competition between the formation and destruction of coronene clusters under interstellar conditions is investigated theoretically. The unimolecular nucleation of neutral clusters is simulated with an atomic model combining an explicit classical force field and a quantum tight-binding approach. Evaporation rates are calculated in the framework of the phase space theory and are inserted in an infrared emission model and compared with the growth rate constants. It is found that, in interstellar conditions, most collisions lead to cluster growth. The time evolution of small clusters (containing up to 312 carbon atoms) was specifically investigated under the physical conditions of the northern photodissociation region of NGC 7023. These clusters are found to be thermally photoevaporated much faster than they are reformed, thus providing an interpretation for the lowest limit of the interstellar cluster size distribution inferred from observations. The effects of ionizing the clusters and density heterogeneities are also considered. Based on our results, the possibility that PAH clusters could be formed in PDRs is critically discussed., 14 pages, 14 figures. Astronomy & Astrophysics, accepted for publication

Published
2006

84. Electronic properties of Francium diatomic compounds and prospects for cold molecule formation

Author

Mireille Aymar, Olivier Dulieu, Fernand Spiegelman, Laboratoire Aimé Cotton (LAC), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11)-École normale supérieure - Cachan (ENS Cachan), Laboratoire de Physique Quantique (LPQ), Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)

Subjects
FOS: Physical sciences, chemistry.chemical_element, 01 natural sciences, 7. Clean energy, Francium, Pseudopotential, [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], Physics - Chemical Physics, 0103 physical sciences, Atom, Physics::Atomic and Molecular Clusters, Physics::Atomic Physics, 010306 general physics, Chemical Physics (physics.chem-ph), Physics, Condensed Matter::Quantum Gases, Quantum Physics, 010304 chemical physics, Condensed Matter Physics, Diatomic molecule, Atomic and Molecular Physics, and Optics, Dipole, chemistry, Excited state, Atomic physics, Quantum Physics (quant-ph), Relativistic quantum chemistry, Valence electron
Abstract

In this work we investigate the possibility to create cold Fr$\_2$, RbFr, and CsFr molecules through photoassociation of cold atoms. Potential curves, permanent and transition dipole moments for the Francium dimer and for the RbFr and RbCs molecules are determined for the first time. The Francium atom is modelled as a one valence electron moving in the field of the Fr$^+$ core, which is described by a new pseudopotential with averaged relativistic effects, and including effective core polarization potential. The molecular calculations are performed for both the ionic species Fr$\_2^+$, RbFr$^+$, CsFr$^+$ and the corresponding neutral, through the CIPSI quantum chemistry package where we used new extended gaussian basis sets for Rb, Cs, and Fr atoms. As no experimental data is available, we discuss our results by comparison with the Rb$\_2$, Cs$\_2$, and RbCs systems. The dipole moment of CsFr reveals an electron transfer yielding a Cs$^+$Fr$^-$ arrangement, while in all other mixed alkali pairs the electron is transferred towards the lighter species. Finally the perturbative treatment of the spin-orbit coupling at large distances predicts that in contrast with Rb$\_2$ and Cs$\_2$, no double-well excited potential should be present in Fr$\_2$, probably preventing an efficient formation of cold dimers via photoassociation of cold Francium atoms.

Published
2006

86. Transition State Spectroscopy of the Photoinduced Ca + CH3F Reaction. 2. Experimental and Ab Initio Studies of the Free Ca***FCH3 Complex

Author

F. Lepetit, Marc-André Gaveau, Fernand Spiegelman, Benoît Soep, M. Collier, C. Sanz Sanz, J. M. Mestdagh, Eric Gloaguen, Laboratoire Francis PERRIN (LFP - URA 2453), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique Quantique (LPQ), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Universidad Autónoma de Madrid (UAM), Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC), and Universidad Autonoma de Madrid (UAM)

Subjects
Reaction mechanism, 010304 chemical physics, Chemistry, Ab initio, Electronic structure, 010402 general chemistry, 01 natural sciences, Molecular physics, 0104 chemical sciences, Pseudopotential, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, Partial charge, Ab initio quantum chemistry methods, Excited state, 0103 physical sciences, Physics::Chemical Physics, Physical and Theoretical Chemistry, Atomic physics, Ground state
Abstract

International audience; The Ca* + CH3F CaF* + CH3 reaction was photoinduced in 1:1 Ca***CH3F complexes formed in a supersonic expansion. The transition state of the reaction was explored by monitoring the electronically excited product, CaF, while scanning the laser that turns on the reaction. Moreover, the electronic structure of the Ca***FCH3 system was studied using ab initio methods by associating a pseudopotential description of the [Ca2+] and [F7+] cores, a core polarization operator on calcium, an extensive Gaussian basis and a treatment of the electronic problem at the CCSD(T) (ground state) and RSPT2 (excited states) level. In this contribution we present experimental results for the free complex and a comparison with the results of a previous experiment where the Ca***CH3F complexes are deposited at the surface of large argon clusters. The ab initio calculations allowed an interpretation of the experimental data in terms of two reaction mechanisms, one involving a partial charge transfer state, the other involving the excitation of the C-F stretch in the CH3F moiety prior to charge transfer.

Published
2006

87. Ultrafast excited state dynamics of the Na3F cluster: quantum wave packet and classical trajectory calculations compared to experimental results

Author

G. Durand, Roland Mitrić, Marie-Catherine Heitz, Vlasta Bonačić-Koutecký, Christoph Meier, Fernand Spiegelman, Laboratoire de Physique Quantique (LPQ), Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC), Théorie (LCAR), Laboratoire Collisions Agrégats Réactivité (LCAR), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Institut fur Chemie, Humboldt-Universität zu Berlin, Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées

Subjects
010304 chemical physics, Chemistry, Wave packet, quantum wave packet, [PHYS.PHYS.PHYS-ATM-PH]Physics [physics]/Physics [physics]/Atomic and Molecular Clusters [physics.atm-clus], General Physics and Astronomy, alkali-halide, dynamics, 01 natural sciences, Photoexcitation, [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], Ab initio quantum chemistry methods, Quantum mechanics, Ionization, Excited state, 0103 physical sciences, Cluster (physics), classical trajectory, Physical and Theoretical Chemistry, Atomic physics, 010306 general physics, Mechanical wave, cluster, theory, Quantum
Abstract

Short-time, excited-state dynamics of the lowest isomer of the Na(3)F cluster is studied theoretically in order to interpret the features of recent time-resolved pump-probe ionization experiments [J. M. L'Hermite, V. Blanchet, A. Le Padellec, B. Lamory, and P. Labastie, Eur. Phys. J. D 28, 361 (2004)]. In the present paper, we propose an identification of the vibrational motion responsible for the oscillations in the ion signal, on the basis of quantum mechanical wave packet propagations and classical trajectory calculations. The good agreement between experiment and theory allows for a clear interpretation of the detected dynamics.

Published
2004

88. Different approaches for the calculation of electronic excited states of nonstoichiometric alkali halide clusters: The example of Na3F

Author

Vlasta Bonačić-Koutecký, Roland Mitrić, Marie-Catherine Heitz, Fernand Spiegelman, Christoph Meier, J. Pittner, G. Durand, Laboratoire de Physique Quantique (LPQ), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Théorie (LCAR), Laboratoire Collisions Agrégats Réactivité (LCAR), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées, Institut für Chemie [HU Berlin], Humboldt-Universität zu Berlin, J. Heyrovsky Institute of Physical Chemistry, Czech Academy of Sciences [Prague] (CAS), Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)

Subjects
ab-initio, 010304 chemical physics, Absorption spectroscopy, potential energy surfaces, Chemistry, General Physics and Astronomy, Multireference configuration interaction, alkali-halide, Electronic structure, 7. Clean energy, 01 natural sciences, Potential energy, Pseudopotential, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, Excited state, 0103 physical sciences, Cluster (physics), Density functional theory, Physical and Theoretical Chemistry, Atomic physics, 010306 general physics, cluster, theory
Abstract

The electronic structure and excited states of the Na(3)F cluster are investigated using different approximate, but numerically efficient, computational schemes, such as a 2e hybrid quantum/classical pseudopotential model with full-configuration interaction or time-dependent density-functional theory. Various quantities such as geometries and transition energies are compared with results previously obtained by multireference configuration interaction calculations, taken as reference data. The potential energy surfaces of the lowest excited states are investigated and the finite-temperature absorption spectra are calculated. The good agreement with recent beam experiments [J.-M. L'Hermite, V. Blanchet, A. Le Padellec, B. Lamory, and P. Labastie, Eur. Phys. J. D 28, 361 (2004)] leads to the conclusion that the absorption spectrum observed experimentally corresponds to the lowest energy isomer which has a C(2v) planar rhombic geometry.

Published
2004

89. Wetting-to-Nonwetting Transition in Metal-CoatedC60

Author

C. Mijoule, Fernand Spiegelman, J. Roques, and Florent Calvo

Subjects
Materials science, 010304 chemical physics, Sodium, Ab initio, General Physics and Astronomy, chemistry.chemical_element, 02 engineering and technology, 021001 nanoscience & nanotechnology, 01 natural sciences, Fullerene molecule, Molecular physics, Metal, chemistry, Homogeneous, visual_art, Electric field, Ionization, 0103 physical sciences, Physics::Atomic and Molecular Clusters, visual_art.visual_art_medium, Physics::Atomic Physics, Wetting, Atomic physics, 0210 nano-technology
Abstract

Based on ab initio and density-functional theory calculations, an empirical potential is proposed to model the interaction between a fullerene molecule and many sodium atoms. This model predicts homogeneous coverage of ${\mathrm{C}}_{60}$ below eight Na atoms and a progressive droplet formation above this size. The effects of ionization, temperature, and external electric field indicate that the various, and apparently contradictory, experimental results can indeed be put into agreement.

Published
2003

90. Nucleation of a sodium droplet on C60

Author

C. Mijoule, Fernand Spiegelman, Florent Calvo, J. Roques, Centre interuniversitaire de recherche et d'ingenierie des matériaux (CIRIMAT), Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC), Laboratoire de Physique Quantique (LPQ), Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Range (particle radiation), Condensed Matter - Materials Science, Materials science, Sodium, Nucleation, chemistry.chemical_element, Materials Science (cond-mat.mtrl-sci), FOS: Physical sciences, Context (language use), Charge (physics), 02 engineering and technology, 021001 nanoscience & nanotechnology, 7. Clean energy, 01 natural sciences, Thermalisation, chemistry, Chemical physics, Electric field, Ionization, 0103 physical sciences, Physics::Atomic and Molecular Clusters, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Atomic physics, 010306 general physics, 0210 nano-technology
Abstract

We investigate theoretically the progressive coating of C60 by several sodium atoms. Density functional calculations using a nonlocal functional are performed for NaC60 and Na2C60 in various configurations. These data are used to construct an empirical atomistic model in order to treat larger sizes in a statistical and dynamical context. Fluctuating charges are incorporated to account for charge transfer between sodium and carbon atoms. By performing systematic global optimization in the size range 18. The separate effects of single ionization and thermalization are also considered, as well as the changes due to a strong external electric field. The present results are discussed in the light of various experimental data., 17 pages, 10 figures

Published
2003

91. Theoretical study of finite temperature spectroscopy in van der Waals clusters. II Time-dependent absorption spectra

Author

Fernand Spiegelman, Florent Calvo, David J. Wales, Laboratoire de Physique Quantique (LPQ), Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Absorption spectroscopy, Gaussian, FOS: Physical sciences, General Physics and Astronomy, 01 natural sciences, Molecular physics, symbols.namesake, Physics - Chemical Physics, 0103 physical sciences, Master equation, Physics - Atomic and Molecular Clusters, Physical and Theoretical Chemistry, 010306 general physics, Spectroscopy, Absorption (electromagnetic radiation), Chemical Physics (physics.chem-ph), Physics, 010304 chemical physics, [PHYS.PHYS.PHYS-ATM-PH]Physics [physics]/Physics [physics]/Atomic and Molecular Clusters [physics.atm-clus], Potential energy, 3. Good health, symbols, Relaxation (physics), [PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph], van der Waals force, Atomic and Molecular Clusters (physics.atm-clus)
Abstract

Using approximate partition functions and a master equation approach, we investigate the statistical relaxation toward equilibrium in selected CaAr$_n$ clusters. The Gaussian theory of absorption (previous article) is employed to calculate the average photoabsorption intensity associated with the 4s^2-> 4s^14p^1 transition of calcium as a function of time during relaxation. In CaAr_6 and CaAr_10 simple relaxation is observed with a single time scale. CaAr_13 exhibits much slower dynamics and the relaxation occurs over two distinct time scales. CaAr_37 shows much slower relaxation with multiple transients, reminiscent of glassy behavior due to competition between different low-energy structures. We interpret these results in terms of the underlying potential energy surfaces for these clusters., 10 pages, 9 figures

Published
2002

92. Exchange Monte Carlo for Molecular Simulations with Monoelectronic Hamiltonians

Author

Florent Calvo, Fernand Spiegelman, Laboratoire de Physique Quantique (LPQ), Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Physics, Condensed Matter - Materials Science, Statistical Mechanics (cond-mat.stat-mech), Quantum Monte Carlo, Monte Carlo method, Materials Science (cond-mat.mtrl-sci), FOS: Physical sciences, General Physics and Astronomy, 02 engineering and technology, 021001 nanoscience & nanotechnology, 01 natural sciences, Hybrid Monte Carlo, 0103 physical sciences, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Dynamic Monte Carlo method, Monte Carlo method in statistical physics, Diffusion Monte Carlo, Kinetic Monte Carlo, Statistical physics, [PHYS.COND.CM-SM]Physics [physics]/Condensed Matter [cond-mat]/Statistical Mechanics [cond-mat.stat-mech], 010306 general physics, 0210 nano-technology, Condensed Matter - Statistical Mechanics, Monte Carlo molecular modeling
Abstract

We introduce a general Monte Carlo scheme for achieving atomistic simulations with monoelectronic Hamiltonians including the thermalization of both nuclear and electronic degrees of freedom. The kinetic Monte Carlo algorithm is used to obtain the exact occupation numbers of the electronic levels at canonical equilibrium, and comparison is made with Fermi-Dirac statistics in infinite and finite systems. The effects of a nonzero electronic temperature on the thermodynamic properties of liquid silver and sodium clusters are presented.

Published
2002

93. Two-electron pseudopotential investigation of the electronic structure of the CaAr molecule

Author

L. Maron, J.-P. Visticot, W. H. Breckenridge, J. M. Mestdagh, Fernand Spiegelman, Laboratoire de Physique Quantique (LPQ), Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC), Laboratoire Francis PERRIN (LFP - URA 2453), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)

Subjects
potential energy surfaces, PACS: 31.25.Nj, 31.50.-x, General Physics and Astronomy, Electronic structure, spin-orbit interactions, 010402 general chemistry, 01 natural sciences, Full configuration interaction, Molecular physics, Pseudopotential, 0103 physical sciences, Physics::Atomic and Molecular Clusters, Physical and Theoretical Chemistry, calcium compounds, 010304 chemical physics, Chemistry, pseudopotential methods, Configuration interaction, ground states, Potential energy, Diatomic molecule, 0104 chemical sciences, configuration interactions, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, Excited state, Atomic physics, Ground state, molecular electronic states
Abstract

International audience; The electronic structure of the Ca-Ar molecule is investigated using [Ca2+] and [Ar] core pseudopotentials complemented by core polarization operators on both atoms, considering the molecule to be a two-electron system. The electronic two-body problem is solved by achieving a full configuration interaction with extensive Gaussian basis sets. The potential energy curves and the molecular constants of all CaAr states dissociating into atomic configurations ranging between the ground state 4s2 1S and the doubly excited state 4p2 3P are determined. Spin-orbit coupling is also included in an atom-in-molecule scheme for states dissociating into the 4s4p and 4s3d configurations. The present theoretical results show good overall agreement with experimental data. They also help to clarify the very complicated spectroscopy of the CaAr system in the 38 000 cm-1 energy range where many states correlated with the 4s4d, 3d4p, and 4p2 atomic configurations interact with or cross one another. As a by-product of the present investigation and with the purpose of checking the pseudopotential accuracy on a simpler related system, low-lying potential energy curves of the single active electron CaAr+ ion are also reported and the corresponding molecular constants are compared with the existing literature.

Published
2002

94. Theoretical study of finite temperature spectroscopy in van der Waals clusters. I. Probing phase changes in CaAr_n

Author

Fernand Spiegelman, M. C. Heitz, Florent Calvo, Laboratoire de Physique Quantique (LPQ), Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Absorption spectroscopy, Quantum superposition, General Physics and Astronomy, FOS: Physical sciences, 01 natural sciences, Molecular physics, Spectral line, symbols.namesake, Physics - Chemical Physics, 0103 physical sciences, Cluster (physics), Physics::Atomic and Molecular Clusters, Physics - Atomic and Molecular Clusters, Physical and Theoretical Chemistry, 010306 general physics, Spectroscopy, Absorption (electromagnetic radiation), Physics, Chemical Physics (physics.chem-ph), 010304 chemical physics, [PHYS.PHYS.PHYS-ATM-PH]Physics [physics]/Physics [physics]/Atomic and Molecular Clusters [physics.atm-clus], Anharmonicity, symbols, [PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph], van der Waals force, Atomic and Molecular Clusters (physics.atm-clus)
Abstract

The photoabsorption spectra of calcium-doped argon clusters CaAr_n are investigated at thermal equilibrium using a variety of theoretical and numerical tools. The influence of temperature on the absorption spectra is estimated using the quantum superposition method for a variety of cluster sizes in the range 6, 17 pages, 9 figures

Published
2002
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95. Electric dipole moments and polarizabilities of single excess electron sodium fluoride clusters: Experiment and theory

Author

Ph. Dugourd, A. Le Padellec, I. Compagnon, Jean-Marc L'Hermite, Fernand Spiegelman, Florent Calvo, Michel Broyer, Driss Rayane, G. Durand, Rodolphe Antoine, Abdul-Rahman Allouche, P. Labastie, Laboratoire de Spectrométrie Ionique et Moléculaire (LASIM), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Agrégats (LCAR), Laboratoire Collisions Agrégats Réactivité (LCAR), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Interactions Ions-Matière (LCAR) (I²M), Laboratoire de Physique Quantique (LPQ), Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées, and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS]Physics [physics], Bond dipole moment, 010304 chemical physics, Chemistry, Transition dipole moment, General Physics and Astronomy, 01 natural sciences, Dipole, Electric dipole moment, Polarization density, Polarizability, 0103 physical sciences, [PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph], Physics::Atomic Physics, Physical and Theoretical Chemistry, Electric dipole transition, Atomic physics, 010306 general physics, Magnetic dipole, ComputingMilieux_MISCELLANEOUS
Abstract

In this article we present the first measurement of the electric dipole susceptibility of one excess electron NanFn–1 clusters. The static electronic polarizability and the permanent electric dipole of these clusters have been calculated with a one-electron model. Experimental values for the susceptibility are clearly related to the calculated values of the permanent dipole. The size evolution of the dipole moments is interpreted in terms of the interplay between the lattice and electron properties. This study outlines that the response of the cluster to the electric field cannot be fully understood with only equilibrium structure calculations and that the coupling between the permanent dipole and the vibrational motion of the cluster has to be taken into account

Published
2002

96. Evidence for trimers evaporation in silver bromide clusters

Author

J.-M. L'Hermite, Franck Rabilloud, Fernand Spiegelman, P. Labastie, Laboratoire Collisions Agrégats Réactivité (LCAR), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique Quantique (LPQ), Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées

Subjects
[PHYS]Physics [physics], Materials science, 010405 organic chemistry, Ab initio, Halide, Trimer, Covalent Interaction, 010402 general chemistry, Silver bromide, 01 natural sciences, Atomic and Molecular Physics, and Optics, 0104 chemical sciences, Pseudopotential, chemistry.chemical_compound, Crystallography, chemistry, Ab initio quantum chemistry methods, Atomic physics, Ground state, ComputingMilieux_MISCELLANEOUS
Abstract

Metastable fragmentation channels of free silver bromide clusters (AgnBrp)+ are reported. The large majority release a neutral trimer (AgBr)3. This is interpreted in the frame of ab initio DFT calculations with 19-electron pseudopotential on silver atom. The stability, the structural and electronic properties of (AgnBrp)(+) (n = 6, p = n, n - 1) are examined. The structures of the clusters are different from expected in electrostatic models. The 3D transition has not yet happened: the calculated ground state structures of (AgBr)n? 6 clusters are quasi two-dimensional. Our work rationalizes the part of covalence in the Ag-Br interaction and the role of d electrons of silver. The known abundance of trimers in the vapor of silver bromide, but also of other silver and cuprous halides is for the first time explained as an indirect consequence of the covalent interaction between metal ions.

Published
2001

97. Études théoriques de la dynamique des états excités de petits agrégats de fluorure de sodium

Author

Christoph Meier, Marie-Catherine Heitz, G. Durand, and Fernand Spiegelman

Subjects
Physics, General Physics and Astronomy, Physical chemistry
Abstract

La dynamique des etats excites des agregats Na 2 F et Na 3 F a ete etudiee par des methodes quantiques de propagation de paquets d'ondes. Les resultats de nos calculs permettent par confrontation avec des donnees experimentales recentes d'elucider la dynamique vibrationnelle dans des etats excites.

Published
2004

98. Theoretical and laboratory spectra of sodium perturbed by molecular hydrogen

Author

J. P. Beaulieu, John F. Kielkopf, Giovanna Tinetti, N. F. Allard, Fernand Spiegelman, Institut d'Astrophysique de Paris (IAP), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), University College of London [London] (UCL), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3)

Subjects
Physics, Opacity, Extrapolation, Astronomy and Astrophysics, Astrophysics, 01 natural sciences, Resonance (particle physics), Spectral line, Dipole, Orders of magnitude (time), Space and Planetary Science, 0103 physical sciences, Radiative transfer, Astrophysics::Earth and Planetary Astrophysics, Atomic physics, 010306 general physics, 010303 astronomy & astrophysics, Line (formation)
Abstract

International audience; We present new unified theory line profiles of neutral Na perturbed by H2. We used a priori Na-H2 potentials, transition dipole moments and validated pseudo-potentials as input to the line shape, and evaluated the profiles for temperatures and densities appropriate for modeling exoplanet and brown dwarf atmospheres. The theory for the resonance lines was compared with new laboratory spectra of sodium to test the validity of the potentials and resulting profiles. The Lorentzian function commonly used to approximate a collisional line profile in radiative transfer calculations is shown to be inadequate, except within a few halfwidths of the line center. In the far wing, the opacity caused by collisions may be several orders of magnitude greater than the extrapolation of the Lorentzian core.

Published
2012

99. Self-consistent field tight-binding model for neutral and (multi-) charged carbon clusters

Author

Fernand Spiegelman, Laurent Montagnon, Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3)

Subjects
010304 chemical physics, Chemistry, General Physics and Astronomy, Electrostatics, 01 natural sciences, Dissociation (chemistry), Spectral line, Ion, Tight binding, Fragmentation (mass spectrometry), Ab initio quantum chemistry methods, 0103 physical sciences, Coulomb, Physical and Theoretical Chemistry, Atomic physics, 010306 general physics, ComputingMilieux_MISCELLANEOUS
Abstract

A semiempirical model for carbon clusters modeling is presented, along with structural and dynamical applications. The model is a tight-binding scheme with additional one- and two-center distance-dependent electrostatic interactions treated self-consistently. This approach, which explicitly accounts for charge relaxation, allows us to treat neutral and (multi-) charged clusters not only at equilibrium but also in dissociative regions. The equilibrium properties, geometries, harmonic spectra, and relative stabilities of the stable isomers of neutral and singly charged clusters in the range n=1-14, for C(20) and C(60), are found to reproduce the results of ab initio calculations. The model is also shown to be successful in describing the stability and fragmentation energies of dictations in the range n=2-10 and allows the determination of their Coulomb barriers, as examplified for the smallest sizes (C(2) (2+),C(3) (2+),C(4) (2+)). We also present time-dependent mean-field and linear response optical spectra for the C(8) and C(60) clusters and discuss their relevance with respect to existing calculations.

Published
2007

100. Rydberg states of small NaArn* clusters

Author

Fernand Spiegelman, Hamid Berriche, Z. Ben Lakhdar, and M. Ben El Hadj Rhouma

Subjects
Chemistry, General Physics and Astronomy, Excimer, Ion, Pseudopotential, symbols.namesake, Excited state, Physics::Atomic and Molecular Clusters, symbols, Rydberg formula, Cluster (physics), Physical and Theoretical Chemistry, van der Waals force, Atomic physics, Ground state
Abstract

The 4s and 5s Rydberg excited states of NaAr(n)* clusters are investigated using a pseudopotential quantum-classical method. While NaAr(n) clusters in their ground state are known to be weakly bound van der Waals complexes with Na lying at the surface of the argon cluster, isomers in 4s or 5s electronically excited states of small NaAr(n)* clusters (nor =10) are found to be stable versus dissociation. The relationship between electronic excitation and cluster geometry is analyzed as a function of cluster size. For both 4s and 5s states, the stable exciplex isomers essentially appear as sodium-centered structures with similar topologies, converging towards those of the related NaAr(n)+ positive ions when the excitation level is increased. This is consistent with a Rydberg-type picture for the electronically excited cluster, described by a central sodium ion solvated by an argon shell, and an outer diffuse electron orbiting around this NaAr(n)+ cluster core.

Published
2006

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