Search

The migration of hole charge created via ionization of the main conformers of the gaseous amino acid glycine is studied. The migration is ultrafast and is mediated solely by many-electron effects, i.e. electronic correlation and relaxation. The influence of the nuclear geometry is investigated by studying the three most abundant conformers of glycine. It is shown that the electron dynamics following ionization can be dramatically different for the different conformers. To facilitate the discussion of the charge migration, the ionization spectra of the conformers are computed as well.

Auger electron spectra recorded in coincidence with two Ar+ ions produced from Ar22+ suggest that the bound one-site two-hole state, Ar2+(3p−2)–Ar, decays further only via radiative charge transfer to the dissociative two-site two-hole states Ar+(3p−1)–Ar+(3p−1). The measured kinetic energy release of Ar22+ agrees well with the theoretical estimate based on this process.

When an excited atom is embedded into an environment, novel relaxation pathways can emerge that are absent for isolated atoms. A well-known example is interatomic Coulombic decay, where an excited atom relaxes by transferring its excess energy to another atom in the environment, leading to its ionization. Such processes have been observed in clusters ionized by extreme-ultraviolet and X-ray lasers. Here, we report on a correlated electronic decay process that occurs following nanoplasma formation and Rydberg atom generation in the ionization of clusters by intense, non-resonant infrared laser fields. Relaxation of the Rydberg states and transfer of the available electronic energy to adjacent electrons in Rydberg states or quasifree electrons in the expanding nanoplasma leaves a distinct signature in the electron kinetic energy spectrum. These so far unobserved electron-correlation-driven energy transfer processes may play a significant role in the response of any nano-scale system to intense laser light., In clusters, relaxation of excited atoms can lead to ionization of nearby atoms, a process known as interatomic Coulomb decay. Here, the authors report on a so far unobserved correlated electronic decay process following Rydberg atom generation in clusters ionized by intense near-infrared fields.

Using inductively coupled plasma–atomic emission spectrometry (ICP-AES), atomic absorption spectrometry (AAS) and instrumental neutron activation analysis (INAA) the concentration of Ag, As, Au, Bi, Cu, Fe, Ga, In, Ni, Sb, Sn, and Zn in 53 samples taken from archaeological finds dated to 4th–2nd century BC and found in the territory of ancient Thracia was determined. Additionally using inductively coupled plasma–mass spectrometry (ICP-MS) and MS for determination of the lead isotope ratios in the samples was carried out. On the basis of these analytical results using cluster analysis for grouping the samples on the bases of the similarity in chemical and isotopic content and the available data from the literature for lead ore deposits in the Balkan Peninsula, the geological origin of the investigated archaeological finds was evaluated. That confirms the expectation that sources of lead might be almost all possible deposits of lead ores on the Balkan Peninsula—from Lavrion through Chalkidiki to the Rhodope mountain. The result indicates that the Thrace did not utilize one single lead source continuously but that lead was provided according to availability from different production centers.

On the basis of numerical, ab initio ΔDF and ΔHF computations of 1s-core, 2s-core, and 2p-core ionization energies of atoms, from Li through Xe, an allometric empirical formula that was proposed for evaluating relativistic corrections (including QED effects) to nonrelativistic values is assessed for homogeneous sets of elements in the periodic table. The two coefficients involved in this formula are precisely determined for 1s-core ionization in the sets of atoms Be-Ne, Mg-Ar, Zn-Kr, and Cd-Xe; 2s-core ionization in the sets of atoms Mg-Ar, Zn-Kr, and Cd-Xe; and 2p-core ionization in the set Mg-Ar. It is shown that the medium relative error on the results obtained using this formula, with respect to those directly computed, decreases from a few percent to a few hundredths of 1% when the depth of the ionized level increases. This formula could be used to include relativistic (and QED) corrections to results yielded by simpler, nonrelativistic calculations on complex molecules involving heavy atoms. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005

In this paper we investigate the variation, along the periodic table, of 2s-core ionization energies, using both relativistic and non-relativistic calculations. We show that electron relaxation energies display variations typical of the shell-filling process, while their relativistic contributions show specifically distorted shell features. Just as for the 1s-core ionization energies, investigated earlier, the sensitivity of these differential properties to the shell-filling process may be used as a probe of the accuracy of calculations of core ionization energies. Discrepancies with experimental results are critically analyzed.

We performed self-consistent calculations of the oscillating part of the ground-state energy of atoms and cations from Be through Ca, using Strutinsky's shell-correction method in the framework of the extended Kohn–Sham scheme. New “transition state” numbers in the Taylor series expansion of the ground-state energy are introduced, allowing the elimination of the second-order shell-correction term. We show that the application of this procedure yields practically identical results whether it is performed self-consistently or not, and even the first-order term of the shell-correction series gives a good approximation. Oscillations in the shell-correction energy of cations appear amplified with respect to those of the corresponding isoelectronic neutral atoms. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004

Highly excited molecular species are at play in the chemistry of interstellar media and are involved in the creation of radiation damage in a biological tissue. Recently developed ultrashort extreme ultraviolet light sources offer the high excitation energies and ultrafast time-resolution required for probing the dynamics of highly excited molecular states on femtosecond (fs) (1 fs=10−15s) and even attosecond (as) (1 as=10−18 s) timescales. Here we show that polycyclic aromatic hydrocarbons (PAHs) undergo ultrafast relaxation on a few tens of femtoseconds timescales, involving an interplay between the electronic and vibrational degrees of freedom. Our work reveals a general property of excited radical PAHs that can help to elucidate the assignment of diffuse interstellar absorption bands in astrochemistry, and provides a benchmark for the manner in which coupled electronic and nuclear dynamics determines reaction pathways in large molecules following extreme ultraviolet excitation., Extreme UV light sources allow us to study the dynamics of excited molecular stets over remarkably short timeframes. Here, the authors probe polyaromatic hydrocarbons—large organic molecules—and show their electronic excitation and subsequent ultrafast relaxation.

International audience; Hole migration is a fascinating process driven by electron correlation, in which purely electronic dynamics occur on a very short time scale in complex ionized molecules, prior to the onset of nuclear motion. However, it is expected that due to coupling to the nuclear dynamics, these oscillations will be rapidly damped and smeared out, which makes experimental observation of the hole migration process rather difficult. In this Letter, we demonstrate that the instantaneous ionization of benzene molecules initiates an ultrafast hole migration characterized by a periodic breathing of the hole density between the carbon ring and surrounding hydrogen atoms on a subfemtosecond time scale. We show that these oscillations survive the dephasing introduced by the nuclear motion for a long enough time to allow their observation. We argue that this offers an ideal benchmark for studying the influence of hole migration on molecular reactivity.

Strutinsky's standard averaging method is applied to metal clusters described by two different potentials—Clemenger–Nilsson (CN) and q-deformed 3-D (Q3D) harmonic oscillator (HO). In addition, a new approximate fitting formula—of the liquid drop model type—is derived for the smooth part of the energy. The results obtained for the oscillating part of the energy (shell correction term) with the two cluster potentials through the two averaging methods are compared and discussed. It is found that with both CN and Q3D HO potentials the standard and approximate methods give similar results for clusters with a large number of particles, whereas for smaller clusters significant differences appear. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002

INAA results of 11 standard reference materials used in archaeometric investigations of pottery as well as in environmental analysis are presented. The values obtained for 24 elements are compared with the certificate values as well as with the analytical data of other investigators. The accuracy of analysis is discussed.

Strutinsky's standard averaging method is formulated in the framework of the extended Kohn–Sham scheme and a two-step procedure permitting the application of the method is proposed. A Taylor-series expansion of the ground-state energy-function of the occupation numbers is derived, which involves the averaged energy as the leading term and shell corrections as smaller terms. Numerical applications for atoms and ions from Be through Ar are presented and discussed. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002

A scheme utilizing excitation of core electrons followed by the resonant-Auger - interatomic Coulombic decay (RA-ICD) cascade was recently proposed as a means of controlling the generation site and energies of slow ICD electrons. This control mechanism was verified in a series of experiments in rare gas dimers. In this article, we present fully ab initio computed ICD electron and kinetic energy release spectra produced following 2p(3/2) → 4s, 2p(1/2) → 4s, and 2p(3/2) → 3d core excitations of Ar in Ar2. We demonstrate that the manifold of ICD states populated in the resonant Auger process comprises two groups. One consists of lower energy ionization satellites characterized by fast interatomic decay, while the other consists of slow decaying higher energy ionization satellites. We show that accurate description of nuclear dynamics in the latter ICD states is crucial for obtaining theoretical electron and kinetic energy release spectra in good agreement with the experiment.

We present a simple approach allowing one to obtain analytical expressions for laser pulses that can drive a two-level system in an arbitrarily chosen way. The proposed scheme relates every desired population-evolution path to a single resonant laser pulse. It allows one to drive the system from any initial superposition of the two states to a final state having the desired distribution of the populations. We exemplify the scheme with a concrete example, where the system is driven from a nonstationary superposition of states to one of its eigenstates. We argue that the proposed approach may have interesting applications for designing pulses that can control ultrafast charge-migration processes in molecules. Although focused on laser-driven population control, the results obtained are general and could be applied for designing other types of control fields.

Resume Dans la note precedente, nous avions exprime l'equation variationnelle d'EulerLagrange relative a l'energie non relativiste de multiplets de spin d'un systeme multifermionique, fonction implicite de la distribution de charge ρ(r), et montre comment la resoudre iterativement — et comment en deduire les valeurs optimales des observables, y compris de la distribution de spin σ(r) — en passant par la fonction scalaire f(r) de la transformation d'echelle locale de l'orbite. Dans la presente note, nous derivons une equation similaire, plus explicite mais aussi plus complexe, pour l'energie totale exprimee comme une fonctionnelle de f(r), et nous comparons les problemes poses par les differentes approches.

A scheme for INAA of native copper, which permits the determination of 22–24 elements is proposed. The possible error source in INAA of native copper and other types of more or less pure copper are evaluated quantitatively. The accuracy and precision of the analyses are tested by comparison with NIST-SRM's. The applicability of the proposed method for archaeometric investigations is demonstrated by the analysis of two samples of native copper and two eneolithic archaeological artifacts from Bulgaria.

Intermolecular Coulombic decay driven by resonant Auger decay can be used to produce low-energy electrons selectively from chosen molecular or atomic sites and with tunable energies, with possible applications in radiation therapy. The irradiation of matter with light tends to electronically excite atoms and molecules. What happens to the resulting excitation energy depends on the nature of the relaxation pathway and the energy of the electrons and ions produced. In one such pathway, known as intermolecular Coulombic decay (ICD), excess energy is transferred to neighbouring atoms or molecules that then lose an electron and become ionized. ICD electrons have relatively low energy, prompting suggestions that they might be harnessed as a form of Auger therapy — cancer treatment that uses large numbers of genotoxic low-energy electrons to damage cancer cells. In a pair of papers [in this issue of Nature] published online this week, Gokhberg et al. propose that ICD can be triggered upon relaxation of an initial resonant core excitation, and Trinter et al. confirm the existence of the proposed excitation experimentally. The efficiency of this relaxation cascade and the fact that it can be tuned to directly control the generation site and the energy of the electrons raise the prospect of the development of more targeted cancer radiotherapy, and possibly new spectroscopic techniques. Irradiation of matter with light tends to electronically excite atoms and molecules, with subsequent relaxation processes determining where the photon energy is ultimately deposited and electrons and ions produced. In weakly bound systems, intermolecular Coulombic decay1 (ICD) enables very efficient relaxation of electronic excitation through transfer of the excess energy to neighbouring atoms or molecules that then lose an electron and become ionized2,3,4,5,6,7,8,9. Here we propose that the emission site and energy of the electrons released during this process can be controlled by coupling the ICD to a resonant core excitation. We illustrate this concept with ab initio many-body calculations on the argon–krypton model system, where resonant photoabsorption produces an initial or ‘parent’ excitation of the argon atom, which then triggers a resonant-Auger-ICD cascade that ends with the emission of a slow electron from the krypton atom. Our calculations show that the energy of the emitted electrons depends sensitively on the initial excited state of the argon atom. The incident energy can thus be adjusted both to produce the initial excitation in a chosen atom and to realize an excitation that will result in the emission of ICD electrons with desired energies. These properties of the decay cascade might have consequences for fundamental and applied radiation biology and could be of interest in the development of new spectroscopic techniques.

Electron correlation, caused by the interaction among electrons in a multielectron system, manifests itself in all states of matter. A complete theoretical description of interacting electrons is challenging; different approximations have been developed to describe the fundamental aspects of the correlation that drives the evolution of simple (few-electron systems in atoms/molecules) as well as complex (multielectron wave functions in atoms, molecules, and solids) systems. Electron correlation plays a key role in the relaxation mechanisms that characterize excited states of neutral or ionized atoms and molecules populated by absorption of extreme ultraviolet (XUV) or X-ray radiation. The dynamics of these states can lead to different processes such as Fano resonance and Auger decay in atoms or interatomic Coulombic decay or charge migration in molecules and clusters. Many of these relaxation mechanisms are ubiquitous in nature and characterize the interaction of complex systems, such as biomolecules, adsorbates on surfaces, and hydrogen-bonded clusters, with XUV light. These mechanisms evolve typically on the femtosecond (1 fs=10(-15) s) or sub-femtosecond timescale. The experimental availability of few-femtosecond and attosecond (1 as=10(-18) s) XUV pulses achieved in the last 10 years offers, for the first time, the opportunity to excite and probe in time these dynamics giving the possibility to trace and control multielectron processes. The generation of ultrashort XUV radiation has triggered the development and application of spectroscopy techniques that can achieve time resolution well into the attosecond domain, thereby offering information on the correlated electronic motion and on the correlation between electron and nuclear motion. A deeper understanding of how electron correlation works could have a large impact in several research fields, such as biochemistry and biology, and trigger important developments in the design and optimization of electronic devices.

We have unambiguously identified interatomic Coulombic decay in NeAr from the inner-valence double-vacancy state $\mathrm{Ne}\mathrm{\text{\ensuremath{-}}}{\mathrm{Ar}}^{2+}(3{s}^{\ensuremath{-}2})$ to outer-valence triple-vacancy states ${\mathrm{Ne}}^{+}(2{p}^{\ensuremath{-}1})\mathrm{\text{\ensuremath{-}}}{\mathrm{Ar}}^{2+}(3{p}^{\ensuremath{-}2})$ by momentum-resolved electron-ion multicoincidence. This is the first observation of interatomic Coulombic decay where three electrons ($3e$) participate. The results suggest that this $3e$ interatomic Coulombic decay is significantly faster than other competing processes like fluorescence decay and charge transfer via curve crossing.

To exploit the high intensity of laser radiation, we propose to select frequencies at which single-photon absorption is of too low energy and two or more photons are needed to produce states of an atom that can undergo interatomic Coulombic decay (ICD) with its neighbors. For Ne dimer it is explicitly demonstrated that the proposed scheme to investigate interatomic processes by multiphoton absorption is much more efficient than with single-photon absorption of sufficiently large frequency as used until now. Extensive calculations on Ne dimer including all the involved nuclear dynamics and the losses by ionization of the participating states show how the low-energy ICD electrons and Ne$^+$ pairs are produced for different laser intensities and pulse durations. At higher intensities the production of Ne$^+$ pairs by successive ionization of the two atoms becomes competitive and the respective emitted electrons interfere coherently with the ICD electrons. It is also demonstrated that a measurement after a time delay can be used to determine the contribution of ICD even at high laser intensity., Comment: 5 figures, Supplemental material file

Using momentum-resolved electron-ion multicoincidence spectroscopy, we have investigated interatomic Coulombic decay (ICD) in the heteronuclear NeAr dimer following Ne $1s$ Auger decay. The measured intensity ratio for the three ICD transitions Ne${}^{2+}$($2{s}^{\ensuremath{-}1}2{p}^{\ensuremath{-}1} {}^{1}P$)Ar to Ne${}^{2+}$($2{p}^{\ensuremath{-}2} {}^{1}S$)--Ar${}^{+}$($3{p}^{\ensuremath{-}1}$), Ne${}^{2+}$($2{s}^{\ensuremath{-}1}2{p}^{\ensuremath{-}1} {}^{1}P$)Ar to Ne${}^{2+}$($2{p}^{\ensuremath{-}2} {}^{1}D$)-Ar${}^{+}$($3{p}^{\ensuremath{-}1}$), and Ne${}^{2+}$($2{s}^{\ensuremath{-}1}2{p}^{\ensuremath{-}1} {}^{3}P$)Ar to Ne${}^{2+}$($2{p}^{\ensuremath{-}2} {}^{3}P$)-Ar${}^{+}$($3{p}^{\ensuremath{-}1}$) reasonably agree with predictions. The kinetic energy release distribution for the fragmentation to Ne${}^{2+}$($2{p}^{\ensuremath{-}2} {}^{1}D$)-Ar${}^{+}$($3{p}^{\ensuremath{-}1}$) after the ICD transition from singlet Ne${}^{2+}$($2{s}^{\ensuremath{-}1}2{p}^{\ensuremath{-}1} {}^{1}P$)Ar state, which is a mirror image of the kinetic energy distribution of the emitted ICD electrons, suggests that the corresponding ICD rate is roughly two times lower than predicted by ab initio calculations.

Electronic many-body effects alone can be the driving force for an ultrafast migration of a positive charge created upon ionization of molecular systems. Here we show that this purely electronic phenomenon generates a characteristic IR radiation. The situation when the initial ionic wave packet is produced by a sudden removal of an electron is also studied. It is shown that in this case a much stronger UV emission is generated. This emission appears as an ultrafast response of the remaining electrons to the perturbation caused by the sudden ionization and as such is a universal phenomenon to be expected in every multielectron system.

We report the first observation of electron-transfer-mediated decay (ETMD) and interatomic Coulombic decay (ICD) from the triply charged states with an inner-valence vacancy, using the Ar dimer as an example. These ETMD and ICD processes, which lead to fragmentation of Ar(3+)-Ar into Ar(2+)-Ar(2+) and Ar(3+)-Ar+, respectively, are unambiguously identified by electron-ion-ion coincidence spectroscopy in which the kinetic energy of the ETMD or ICD electron and the kinetic energy release between the two fragment ions are measured in coincidence.

The time-dependent theory of an atomic cascade decay process is discussed. We show that it is useful to measure the spectra of the emitted particles (electrons or photons) as a function of time and introduce time-dependent spectra and time-dependent coincidence spectra. The analysis reveals that there are several timescales involved in the atomic cascades and in the respective spectra. The work prepares the ground for the discussion of molecules, clusters, and solids, where the nuclear dynamics strongly participate in the cascade decay process making it much more complex.

An ultrafast mechanism belonging to the family of interatomic Coulombic decay (ICD) phenomena is proposed. When two excited species are present, an ultrafast energy transfer can take place bringing one of them to its ground state and ionizing the other one. It is shown that if large homoatomic clusters are exposed to an ultrashort and intense laser pulse whose photon energy is in resonance with an excitation transition of the cluster constituents, the large majority of ions will be produced by this ICD mechanism rather than by two-photon ionization. A related collective-ICD process that is operative in heteroatomic systems is also discussed., Comment: 4 pages, 3 figures

Low-lying relaxation satellites give rise to ultrafast electron dynamics following outer-valence ionization of a molecular system is studied. To demonstrate the impact of such satellites, the evolution of the electronic cloud after sudden removal of an electron from the highest occupied molecular orbital (HOMO) of the organic unsaturated nitroso compound 2-Nitroso[1,3]oxazolo[5,4-d][1,3]oxazole is traced in real time and space using ab initio methods only. Our results show that the initially created hole charge remains stationary but on top of it the system reacts by an ultrafast pi-pi* excitation followed by a cyclic excitation-deexcitation process which leads to a redistribution of the charge. The pi-pi* excitation following the removal of the HOMO electron takes place on a sub-femtosecond time scale and the period of the excitation-deexcitation alternations is about 1.4 fs. In real space the processes of excitation and de-excitation represent ultrafast delocalization and localization of the charge. The results are analyzed by a simple two- and three-state model., Comment: 8 pages, 5 figures

Triggered by the interest to study charge migration in large molecular systems, a simple methodology has recently been proposed based on straightforward density functional theory calculations. This approach describes the time evolution of the initially created hole density in terms of the time evolution of the ionized highest occupied molecular orbital (HOMO). Here we demonstrate that this time-dependent analog of Koopmans’ theorem is not valid, and instead of the time evolution of the HOMO, the time evolution of the orbitals that remain occupied in the cation determines the evolution of the initially created hole in the framework of time-dependent single-determinant theories. Numerical examples underline that for a proper description of charge migration processes, an explicit treatment of the electron correlation is indispensable. Moreover, they also demonstrate that the attempts to describe charge migration based on Kohn–Sham density functional theory using conventional exchange-correlation functionals are doomed to fail due to the well-known self-interaction error.

Electron correlation can be the driving force for ultrafast charge migration. Using ab initio calculations in the present work we demonstrate that the positive charge created by ionization out of an inner- or outer-valence shell of an oligopeptide can migrate throughout the system within just few femtoseconds.

We analyze in detail the accessible relaxation pathways via electron emission of the Ne2+Ar states populated via the K-LL Auger decay of Ne+(1s−1)Ar. In particular, we concentrate on the “direct” interatomic Coulombic decay (ICD) of the Ne2+(2s−12p−1)Ar weakly bound doubly ionized states into the manifold of the Ne2+(2p−2)–Ar+(3p−1) repulsive triply ionized ones. To carry out the present study the potential energy curves of the NeAr ground state, the core ionized state Ne+(1s−1)Ar, the relevant dicationic and tricationic states, and the corresponding ICD transition rates have been computed using accurate ab initio methods and basis sets. The total and partial ICD electron spectra are computed within the framework of the time-dependent theory of wave packet propagation. Thereby, the impact of nuclear dynamics accompanying the electronic decay on the computed ICD-electron spectra is investigated in detail.

Potential energy curves of the Auger state Ar+(2p(-1))-Ar, the different one- and two-site dicationic states Ar2 ++ (with energies in the range of 32-77 eV), and the lowest two-site tricationic states Ar++ - Ar+ (with energies in the range of 64-76 eV) computed using elaborated ab initio methods are reported. The accessible relaxation channels of the electronic states of Ar++ - Ar populated by Auger decay are studied. In particular, we study in detail the interatomic Coulombic decay following the population of one-site satellite states of Ar++(3s(-1)3p(-1))-Ar recently observed experimentally. Other relaxation pathways of Ar++ - Ar, including radiative charge transfer, nuclear dynamics through curve crossing, and intra-atomic decay processes are also investigated.

The accessible relaxation channels of the electronic states of Ne++-Ne and Ne3+-Ne populated by KLL Auger decay are studied. In particular, we address the "direct" and "exchange" interatomic Coulombic decays (ICDs) and the electron-transfer-mediated decay following the population of one-site states Ne++(2s(-2))-Ne and Ne++(2s(-1)2p(-1) P-1)-Ne. Radiative charge transfer of the low lying Ne++(2p(-2))-Ne states, three-electron ICD process from the Ne++(2s(-2))-Ne states, as well as charge transfer at the points of curve crossing of the lowest in energy Ne3+(2p(-3))-Ne states are also discussed. To carry out the present study, we have calculated the potential energy curves (from 1.75 to 5.00 angstrom) of the ground state Ne-2, the core ionized state Ne+(1s(-1))-Ne, and the dicationic and tricationic states with energies in the range of 45-140 eV using accurate ab initio methods and basis sets. Apart from being of interest by themselves, the results obtained may be helpful in interpreting the recent measurements of interatomic electronic processes following Auger decay in neon dimer [K. Kreidi , J. Phys. B 41, 101002 (2008)]. (C) 2008 American Institute of Physics.

We report on a novel correlated electronic decay process following extensive Rydberg atom formation in clusters ionized by intense near-infrared fields. A peak close to the atomic ionization potential is found in the electron kinetic energy spectrum. This new contribution is attributed to an energy transfer between two electrons, where one electron decays from a Rydberg state to the ground state and transfers its excess energy to a weakly bound cluster electron in the environment that can escape from the cluster. The process is a result of nanoplasma formation and is therefore expected to be important, whenever intense laser pulses interact with nanometer-sized particles.

We report on the observation of a novel intracluster Coulombic decay process following Rydberg atom formation in clusters ionized by intense near-infrared fields. A new decay channel emerges, in which a Rydberg atom relaxes to the ground state by transferring its excess energy to a weakly bound electron in the environment that is emitted from the cluster. We find evidence for this process in the electron spectra, where a peak close to the corresponding atomic ionization potential is observed. For Ar clusters, a decay time of 87 ps is measured, which is significantly longer than in previous time-resolved studies of interatomic Coulombic decay.

Due to electronic many-body effects, the ionization of a molecule can trigger ultrafast electron dynamics appearing as a migration of the created hole charge throughout the system. Here we propose a scheme for control of the charge migration dynamics with a single ultrashort laser pulse. We demonstrate by fully ab initio calculations on a molecule containing a chromophore and an amine moieties that simple pulses can be used for stopping the charge-migration oscillations and localizing the charge on the desired site of the system. We argue that this control may be used to predetermine the follow-up nuclear rearrangement and thus the molecular reactivity.

Tremendous advances in laser pump-probe techniques open the door for the observation in real time of ultrafast \textit{electronic} processes. Particularly attractive is the visualization of interatomic processes where one can follow the process of energy transfer from one atom to another. The interatomic Coulombic decay (ICD) provides such a process which is abundant in nature. A multielectron wavepacket propagation method enables now to trace fully ab initio the electron dynamics of the process in real time and in space taking into account all electrons of the system and their correlations. The evolution of the electronic cloud throughout the ICD process in the rare gas cluster NeAr following Ne2s ionization is computed and analyzed. The process takes place on a femtosecond timescale, and a surprisingly strong response is found at a much shorter attosecond timescale., 5 pages, 3 figures

The local-scaling transformation (LST) variational method is used to derive an energy functional which depends on R dynamical variables, the LST functions realizing the transformation of the R orbitals involved in the expansion of the model N-fermion wave function. The solution of the Euler-Lagrange system with respect to these variables leads to the determination of approximate ground-state properties for the considered system. A set of atomic and molecular problems is discussed.

In the formalism of reduced density matrices and functions, using the irreducible tensor-operator technique and the space-spin separation scheme, the matrix elements of one of the main spin-relativistic corrections of the Breit-Pauli Hamiltonian, the spin-orbit interactions, are expressed in a form suitable for numeric implementation. A comparison with other methods is made and the advantages of such an approach are discussed.

In order to clarify the conditions under which the staggering phenomenon may occur in diatomic molecules and get more hints on its physical origin, we have investigated the behavior of the fourth-order finite difference E 1(iv) (J) of rotational transition energies, with respect to quantum number J (staggering pattern), for a few rovibrational bands of heteronuclear diatomics involving nuclear isotopes, using accurate optical and infrared data from the literature. For the upper and lower bands of 63CuH, the sign alternation characterizing ΔJ= 1 staggering appears slightly larger than the errors induced by the measurement and calculation processes, while for the upper and lower bands of 63CuD and 65CuD it remains within the error bars. For the bands we have investigated in the carbon monoxide molecule there seems to be some staggering underlying rather large errors in 12C16O while in 12C18O there appears no significant staggering.

The resonant-Auger - interatomic Coulombic decay (ICD) cascade was recently suggested as an efficient means of controlling the course of the ICD process. Recent theoretical and experimental works show that control over the energies of the emitted ICD electrons can be achieved either by varying the photon energy to produce different initial core excitations or by changing the neighboring species. This work presents a theoretical investigation on the role of the rare-gas neighbor and clarifies how the latter influences the ICD process. For this purpose, we compare fully ab initio computed ICD-electron and kinetic energy release spectra following the 2p(3/2) → 4s, 2p(1/2) → 4s and 2p(3/2) → 3d of Ar in ArKr and Ar2. We demonstrate that the presence of the chemically "softer" partner atom results in an increase in the energies of the emitted ICD electrons, and also in the appearance of additional ICD-active states. The latter leads to a threefold increase in the ICD yield for the case of the 2p(3/2, 1/2) → 4s parent core excitations.

Exposing molecules to ultrashort laser pulses creates electronic wave packets, and therefore, triggers pure electron dynamics in the excited or ionized system. In the case of ionization, these dynamics may manifest as a migration of the initially created localized hole throughout the system and were termed charge migration. Here, we review the theoretical foundation and the most important results obtained in the study of the charge migration phenomenon, as well as give some perspectives for the directions the future studies could go.

In this paper we review the main properties of the q -deformed, 3-dimensional harmonic oscillator ( Q3O ) and show how this model can be used for the description of metal cluster properties. We recall that the Q3O symmetry u q (3) ⊃ so q (3), which is a non-linear deformation of the chain u(3) ⊃ so(3) , is a relevant symmetry for metal clusters. This is because the Q3O potential gathers the main features of semi-empirical potentials (such as that of Nilsson and Clemenger) which have been successfully used in the description of metal clusters. The advantage of our model is that the class of q -deformed symmetries is richer than that of Lie symmetries, making the Q30 potential more flexible than its classical analogs. We show how to derive potentials which, when put into the “standard” Schrodinger equation, provide a spectrum similar to the Q3O model. We also introduce prescriptions for choosing the parameters τ and δ of the model, thus closing the procedure for obtaining magic numbers. A good agreement is found between the magic numbers obtained through our model and the experimental results.

Core excitation energies (CEs) are known to depend on the chemical environment mostly through the charge transfered from or to the would-be excited atom in the ground-state molecule. We have made use of this peculiarity to set up a combined method for evaluating the CEs of molecules involving heavy atoms, where cumulated handicaps make direct calculations very difficult. We have evaluated the CEs of np levels in chromium, molybdenum and tungsten hexafluorides and compared the contributions of relaxation and relativity. In a first step, various approximate methods were used to evaluate the amount of charge transfered in the three hexafluorides, using the experimental geometries and testing different definitions of the charge. Results show the following trends: i) the calculated charge transfer increases as CrF 6 ≪ MoF 6 6 ; ii) Mulliken (balanced) charges vary in the order REX ≫ RHF > CISD > DFT, and Weinhold (natural) charges tend to be slightly larger; iii) our best (CISD) calculations give a natural percentage of electron transfer from the metal atom to the bonded fluorines of about 45% for CrF 6 , 56% for MoF 6 , and 59% for WF 6 . In a second step, numerical ab-initio , relativistic, ΔDF calculations of the total and orbital energies were performed on the ground-state and core-excited metal ions involving 1 to 5 valence ionizations. Core excitation energies were deduced and the relative importance of relaxation and relativity effects was discussed. In a last step, the core excitation energies for the molecules were evaluated by interpolating between values previously obtained for the free ions, using the net atomic charges derived for the ground-state molecules in our best previous approximation. The results are particularly striking for WF 6 : 1) for core excitations from the 2p 1/2 , 2p 3/2 and 3p 1/2 , 3p 3/2 levels, experimental energies are reproduced within 0.4–1.2 eV; 2) there is a relaxation alteration of the charge transfer stronger for the 3p than for the 2p levels; 3) relativistic corrections are much larger than and opposite to relaxation corrections.

Trace analysis of environmental materials is a complex process including not only the analysis itself but also sampling, sample preparation, physical and chemical pretreatment and data evaluation. Therefore the basic rules for sampling of environmental materials and methods for preconcentration are presented. The possibilities and potential of the most significant methods for environmental trace analysis (X-ray fluorescence (XRF), inductively coupled plasma-mass spectrometry (ICP-MS), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), atomic absorption spectrometry (AAS), instrumental neutron activation analysis (INAA), electrochemical methods and methods measuring radionuclides) are discussed and comparative evaluation is done. The methods for speciation of metals in environmental matrices are briefly presented. Since there is not a single method that can solve all tasks in environmental investigations a combination of at least two methods might be recommended.

Strutinsky's method for performing a consistent decomposition of the binding energy of a quantum system into averaged and oscillating parts is presented and used to derive a self-consistent averaging procedure (SCAP) in the Hartree-Fock-Roothaan (HFR) scheme. This procedure is applied to atoms from Be to Zn, using their HFR one-electron energies, which shows that the application of Strutinsky's method to atoms requires an accurate determination of that part of the energy spectrum responsible for shell effects. It is shown that SCAP would be a precise tool for splitting an energy space into core and valence parts and for defining and extracting shell effects in such energetic properties as ionization potentials.

Excitation of two identical species in a cluster by the absorption of two photons of the same energy is strongly suppressed since the excitation of one subunit blocks the excitation of the other one due to the binding Coulomb interaction. Here, we propose a very efficient way to overcome this blockade in producing doubly-excited homoatomic clusters by a single intense laser pulse. For Ne$_2$ it is explicitly demonstrated that the optimal carrier frequency of the pulse is given by half of the energy of the target state, which allows one to doubly excite more than half of the dimers at moderate field intensities. These dimers then undergo ultrafast interatomic decay bringing one Ne to its ground state and ionizing the other one. The reported \emph{ab initio} electron spectra present reliable predictions for future experiments by strong laser pulses., Comment: 5 figs