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1. Observation of Multiple Ordered Solvation Shells in Doped Helium Droplets: The Case of HeNCa2

Author

Ministerio de Ciencia e Innovación (España), Austrian Science Fund, Zunzunegui-Bru, Eva [0000-0002-0293-0266], Gruber, Elisabeth [0000-0002-1195-3638], Bartolomei, Massimiliano [0000-0001-8643-4106], Hernández, Marta I. [0000-0003-3963-4345], Campos-Martínez, José [0000-0002-8848-6353], González-Lezana, Tomás [0000-0003-0010-5219], Zappa, Fabio [0000-0003-4452-8520], Scheier, Paul [0000-0002-7480-6205], Pérez de Tudela, Ricardo [0000-0002-0314-6983], Hernández-Rojas, Javier [0000-0003-0610-660X], Zunzunegui-Bru, Eva, Gruber, Elisabeth, Lázaro, Teresa, Bartolomei, Massimiliano, Hernández, Marta I., Campos-Martínez, José, González-Lezana, Tomás, Bergmeister, Stefan, Zappa, Fabio, Scheier, Paul, Pérez de Tudela, Ricardo, Hernández-Rojas, Javier, Bretón, José, Ministerio de Ciencia e Innovación (España), Austrian Science Fund, Zunzunegui-Bru, Eva [0000-0002-0293-0266], Gruber, Elisabeth [0000-0002-1195-3638], Bartolomei, Massimiliano [0000-0001-8643-4106], Hernández, Marta I. [0000-0003-3963-4345], Campos-Martínez, José [0000-0002-8848-6353], González-Lezana, Tomás [0000-0003-0010-5219], Zappa, Fabio [0000-0003-4452-8520], Scheier, Paul [0000-0002-7480-6205], Pérez de Tudela, Ricardo [0000-0002-0314-6983], Hernández-Rojas, Javier [0000-0003-0610-660X], Zunzunegui-Bru, Eva, Gruber, Elisabeth, Lázaro, Teresa, Bartolomei, Massimiliano, Hernández, Marta I., Campos-Martínez, José, González-Lezana, Tomás, Bergmeister, Stefan, Zappa, Fabio, Scheier, Paul, Pérez de Tudela, Ricardo, Hernández-Rojas, Javier, and Bretón, José

Abstract

In this Letter, we report the experimental detection of likely the largest ordered structure of helium atoms surrounding a monatomic impurity observed to date using a recently developed technique. The mass spectrometry investigation of HeNCa2+ clusters, formed in multiply charged helium nanodroplets, reveals magic numbers at N = 12, 32, 44, and 74. Classical optimization and path integral Monte Carlo calculations suggest the existence of up to four shells surrounding the calcium dication which are closed with well-ordered Mozartkugel-like structures: He12Ca2+ with an icosahedron, the second at He32Ca2+ with a dodecahedron, the third at He44Ca2+ with a larger icosahedron, and finally for He74Ca2+, we find that the outermost He atoms form an icosidodecahedron which contains the other inner shells. We analyze the reasons for the formation of such ordered shells in order to guide the selection of possible candidates to exhibit a similar behavior.

Published
2023

2. Solvation of cationic copper clusters in molecular hydrogen

Author

Ministerio de Ciencia e Innovación (España), Consejo Superior de Investigaciones Científicas (España), Centro de Supercomputación de Galicia, Austrian Science Fund, European Cooperation in Science and Technology, Lushchikova, O. V. [0000-0002-5699-6818], Reichegger, J. [0009-0003-2040-3501], Kollotzek, S. [0000-0002-0732-4919], Zappa, F. [0000-0003-4452-8520], Mahmoodi-Darian, M. [0000-0003-4350-4770], #NODATA#, Campos-Martínez, José [0000-0002-8848-6353], González-Lezana, Tomás [0000-0003-0010-5219], Pirani, F. [0000-0003-3110-6521], Scheier, P. [0000-0002-7480-6205], Lushchikova, O. V., Reichegger, J., Kollotzek, S., Zappa, F., Mahmoodi-Darian, M., Bartolomei, Massimiliano, Campos-Martínez, José, González-Lezana, Tomás, Pirani, F., Scheier, P., Ministerio de Ciencia e Innovación (España), Consejo Superior de Investigaciones Científicas (España), Centro de Supercomputación de Galicia, Austrian Science Fund, European Cooperation in Science and Technology, Lushchikova, O. V. [0000-0002-5699-6818], Reichegger, J. [0009-0003-2040-3501], Kollotzek, S. [0000-0002-0732-4919], Zappa, F. [0000-0003-4452-8520], Mahmoodi-Darian, M. [0000-0003-4350-4770], #NODATA#, Campos-Martínez, José [0000-0002-8848-6353], González-Lezana, Tomás [0000-0003-0010-5219], Pirani, F. [0000-0003-3110-6521], Scheier, P. [0000-0002-7480-6205], Lushchikova, O. V., Reichegger, J., Kollotzek, S., Zappa, F., Mahmoodi-Darian, M., Bartolomei, Massimiliano, Campos-Martínez, José, González-Lezana, Tomás, Pirani, F., and Scheier, P.

Abstract

Multiply charged superfluid helium nanodroplets are utilized to facilitate the growth of cationic copper clusters (Cun+, where n = 1-8) that are subsequently solvated with up to 50 H2 molecules. Production of both pristine and protonated cationic Cu clusters are detected mass spectrometrically. A joint effort between experiment and theory allows us to understand the nature of the interactions determining the bonding between pristine and protonated Cu+ and Cu2+ cations and molecular hydrogen. The analysis reveals that in all investigated cationic clusters, the primary solvation shell predominantly exhibits a covalent bonding character, which gradually decreases in strength, while for the subsequent shells an exclusive non-covalent behaviour is found. Interestingly, the calculated evaporation energies associated with the first solvation shell markedly surpass thermal values, positioning them within the desirable range for hydrogen storage applications. This comprehensive study not only provides insights into the solvation of pristine and protonated cationic Cu clusters but also sheds light on their unique bonding properties.

Published
2023

3. Trihydrogen Cation Helium Clusters: A New Potential Energy Surface

Author

Ministerio de Ciencia e Innovación (España), Bretón, José [0000-0003-2637-2876], Hernández-Rojas, Javier [0000-0003-0610-660X], Hernández, Marta I. [0000-0003-3963-4345], Campos-Martínez, José [0000-0002-8848-6353], González-Lezana, Tomás [0000-0003-0010-5219], Bretón, José, Hernández-Rojas, Javier, Hernández, Marta I., Campos-Martínez, José, González-Lezana, Tomás, Ministerio de Ciencia e Innovación (España), Bretón, José [0000-0003-2637-2876], Hernández-Rojas, Javier [0000-0003-0610-660X], Hernández, Marta I. [0000-0003-3963-4345], Campos-Martínez, José [0000-0002-8848-6353], González-Lezana, Tomás [0000-0003-0010-5219], Bretón, José, Hernández-Rojas, Javier, Hernández, Marta I., Campos-Martínez, José, and González-Lezana, Tomás

Abstract

We present a new analytical potential energy surface (PES) for the interaction between the trihydrogen cation and a He atom, H3+-He${{H}_{3}^{+}-He}$ , in its electronic ground state. The proposed PES has been built as a sum of two contributions: a polarization energy term due to the electric field generated by the molecular cation at the position of the polarizable He atom, and an exchange-repulsion and dispersion interactions represented by a sum of "atom-bond" potentials between the three bonds of H3+${{H}_{3}^{+}}$ and the He atom. All parameters of this new PES have been chosen and fitted from data obtained from high-level ab-initio calculations. Using this new PES plus the Aziz-Slaman potential for the interaction between Helium atoms and assuming pair-wise interactions, we carry out classical Basin-Hopping (BH) global optimization, semiclassical BH with Zero Point Energy corrections, and quantum Diffusion Monte Carlo simulations. We have found the minimum energy configurations of small He clusters doped with H3+${{H}_{3}^{+}}$ , H3+HeN${{H}_{3}^{+}{\left(He\right)}_{N}}$ , with N=1-16. The study of the energies of these clusters allows us to find a pronounced anomaly for N=12, in perfect agreement with previous experimental findings, which we relate to a greater relative stability of this aggregate.

Published
2023

4. Ar+ ArH+ Reactive Collisions of Astrophysical Interest: The Case of 36 Ar

Author

Ministerio de Ciencia e Innovación (España), Comunidad de Madrid, Prosmiti, Rita [0000-0002-1557-1549], González-Lezana, Tomás [0000-0003-0010-5219], Koner, Debasish [0000-0002-5116-4908], Montes de Oca, Judit, Darna, Beatriz, García-Ruiz, Borja, Prosmiti, Rita, González-Lezana, Tomás, Koner, Debasish, Ministerio de Ciencia e Innovación (España), Comunidad de Madrid, Prosmiti, Rita [0000-0002-1557-1549], González-Lezana, Tomás [0000-0003-0010-5219], Koner, Debasish [0000-0002-5116-4908], Montes de Oca, Judit, Darna, Beatriz, García-Ruiz, Borja, Prosmiti, Rita, González-Lezana, Tomás, and Koner, Debasish

Abstract

The reactive collision between 36 Ar and the 36 ArH+ species has been investigated by means of quantum mechanical (QM), quasiclassical trajectories (QCT) and statistical quantum mechanical (SQM) approaches. Reaction probabilities, cross sections as a function of the energy and rate constants in terms of the temperature have been obtained. Cumulative distributions as a function of the collision time and the inspection of selected QCT corresponding to specific dynamical mechanisms have been analysed. Predictions by means of the SQM method are in good agreement with the QM results, thus supporting the complex-forming nature of the process.

Published
2023

5. Helium nanodroplets as an efficient tool to investigate hydrogen attachment to alkali cations

Author

Austrian Science Fund, Ministerio de Ciencia e Innovación (España), Ministerio de Economía y Competitividad (España), Consejo Superior de Investigaciones Científicas (España), Centro de Supercomputación de Galicia, Kollotzek, Siegfried [0000-0002-0732-4919], Campos-Martínez, José [0000-0002-8848-6353], Bartolomei, Massimiliano [0000-0001-8643-4106], Pirani, Fernando [0000-0003-3110-6521], Hernández, Marta I. [0000-0003-3963-4345], Zunzunegui-Bru, Eva [0000-0002-0293-0266], González-Lezana, Tomás [0000-0003-0010-5219], Hernández-Rojas, Javier [0000-0003-0610-660X], Echt, Olof [0000-0002-0970-1191], Scheier, Paul [0000-0002-7480-6205], Kollotzek, Siegfried, Campos-Martínez, José, Bartolomei, Massimiliano, Pirani, Fernando, Tiefenthaler, Lukas, Hernández, Marta I., Lázaro, Teresa, Zunzunegui-Bru, Eva, González-Lezana, Tomás, Bretón, José, Hernández-Rojas, Javier, Echt, Olof, Scheier, Paul, Austrian Science Fund, Ministerio de Ciencia e Innovación (España), Ministerio de Economía y Competitividad (España), Consejo Superior de Investigaciones Científicas (España), Centro de Supercomputación de Galicia, Kollotzek, Siegfried [0000-0002-0732-4919], Campos-Martínez, José [0000-0002-8848-6353], Bartolomei, Massimiliano [0000-0001-8643-4106], Pirani, Fernando [0000-0003-3110-6521], Hernández, Marta I. [0000-0003-3963-4345], Zunzunegui-Bru, Eva [0000-0002-0293-0266], González-Lezana, Tomás [0000-0003-0010-5219], Hernández-Rojas, Javier [0000-0003-0610-660X], Echt, Olof [0000-0002-0970-1191], Scheier, Paul [0000-0002-7480-6205], Kollotzek, Siegfried, Campos-Martínez, José, Bartolomei, Massimiliano, Pirani, Fernando, Tiefenthaler, Lukas, Hernández, Marta I., Lázaro, Teresa, Zunzunegui-Bru, Eva, González-Lezana, Tomás, Bretón, José, Hernández-Rojas, Javier, Echt, Olof, and Scheier, Paul

Abstract

We report a novel method to reversibly attach and detach hydrogen molecules to positively charged sodium clusters formed inside a helium nanodroplet host matrix. It is based on the controlled production of multiply charged helium droplets which, after picking up sodium atoms and exposure to H2 vapor, lead to the formation of Nam+(H2)n clusters, whose population was accurately measured using a time-of-flight mass spectrometer. The mass spectra reveal particularly favorable Na+(H2)n and Na2+(H2)n clusters for specific “magic” numbers of attached hydrogen molecules. The energies and structures of these clusters have been investigated by means of quantum-mechanical calculations employing analytical interaction potentials based on ab initio electronic structure calculations. A good agreement is found between the experimental and the theoretical magic numbers.

Published
2022

6. Complexes of Alkali Metal Cations and Molecular Hydrogen: Potential Energy Surfaces and Bound States

Author

Ministerio de Economía y Competitividad (España), Ministero dell'Istruzione, dell'Università e della Ricerca, Università degli Studi di Perugia, Centro de Supercomputación de Galicia, Bartolomei, Massimiliano [0000-0001-8643-4106], González-Lezana, Tomás [0000-0003-0010-5219], Campos-Martínez, José [0000-0002-8848-6353], Hernández, Marta I. [0000-0003-3963-4345], Pirani, Fernándo [0000-0003-3110-6521], Bartolomei, Massimiliano, González-Lezana, Tomás, Campos-Martínez, José, Hernández, Marta I., Pirani, Fernando, Ministerio de Economía y Competitividad (España), Ministero dell'Istruzione, dell'Università e della Ricerca, Università degli Studi di Perugia, Centro de Supercomputación de Galicia, Bartolomei, Massimiliano [0000-0001-8643-4106], González-Lezana, Tomás [0000-0003-0010-5219], Campos-Martínez, José [0000-0002-8848-6353], Hernández, Marta I. [0000-0003-3963-4345], Pirani, Fernándo [0000-0003-3110-6521], Bartolomei, Massimiliano, González-Lezana, Tomás, Campos-Martínez, José, Hernández, Marta I., and Pirani, Fernando

Abstract

Complexes between metal cations and molecular hydrogen are systems quite amenable for precise spectroscopic and theoretical studies, and at the same time, they are relevant for applications in hydrogen storage and astrochemistry. In this work, we report new intermolecular potential energy surfaces and rovibrational states calculations for complexes involving molecular hydrogen and alkaline metal cations, M+−H2 (M+ = Na+, K+, Rb+, Cs+). The intermolecular potentials, formulated in an internally consistent way to emphasize differences in the properties of the systems, are represented by simple analytical expressions whose parameters have been optimized from comparison with accurate ab initio calculations. Properties of the low-lying bound statesbinding energies, frequencies, and rotational constantsare compared with previous measurements or computations and an overall good agreement is achieved, supporting the reliability of the present formulation. Variations of these properties as a function of the cation size and isotopic substitution, with a proper sequence of ortho and para rotational levels, are also discussed.

Published
2019

7. A combined experimental and theoretical investigation of Cs+ ions solvated in HeN clusters

Author

Austrian Science Fund, European Commission, Ministerio de Industria y Competitividad (España), Pérez de Tudela, Ricardo [0000-0002-0314-6983], Scheier, Paul [0000-0002-7480-6205], Pirani, F. [0000-0003-3110-6521], Hernández-Rojas, Javier [0000-0003-0610-660X], Bretón, José [0000-0003-2637-2876], Bartolomei, Massimiliano [0000-0001-8643-4106], González-Lezana, Tomás [0000-0003-0010-5219], Hernández, Marta I. [0000-0003-3963-4345], Campos-Martínez, José [0000-0002-8848-6353], Villarreal, Pablo [0000-0003-4710-9268], Pérez de Tudela, Ricardo, Martini, Paul, Goulart, Marcelo, Scheier, Paul, Pirani, F., Hernández-Rojas, Javier, Bretón, José, Ortiz de Zárate, J., Bartolomei, Massimiliano, González-Lezana, Tomás, Hernández, Marta I., Campos-Martínez, José, Villarreal, Pablo, Austrian Science Fund, European Commission, Ministerio de Industria y Competitividad (España), Pérez de Tudela, Ricardo [0000-0002-0314-6983], Scheier, Paul [0000-0002-7480-6205], Pirani, F. [0000-0003-3110-6521], Hernández-Rojas, Javier [0000-0003-0610-660X], Bretón, José [0000-0003-2637-2876], Bartolomei, Massimiliano [0000-0001-8643-4106], González-Lezana, Tomás [0000-0003-0010-5219], Hernández, Marta I. [0000-0003-3963-4345], Campos-Martínez, José [0000-0002-8848-6353], Villarreal, Pablo [0000-0003-4710-9268], Pérez de Tudela, Ricardo, Martini, Paul, Goulart, Marcelo, Scheier, Paul, Pirani, F., Hernández-Rojas, Javier, Bretón, José, Ortiz de Zárate, J., Bartolomei, Massimiliano, González-Lezana, Tomás, Hernández, Marta I., Campos-Martínez, José, and Villarreal, Pablo

Abstract

Solvation of Cs+ ions inside helium droplets has been investigated both experimentally and theoretically. On the one hand, mass spectra of doped helium clusters ionized with a crossed electron beam, HeNCs+, have been recorded for sizes up to N = 60. The analysis of the ratio between the observed peaks for each size N reveals evidences of the closure of the first solvation shell when 17 He atoms surround the alkali ion. On the other hand, we have obtained energies and geometrical structures of the title clusters by means of basin-hopping, diffusion Monte Carlo (DMC), and path integral Monte Carlo (PIMC) methods. The analytical He–Cs+ interaction potential employed in our calculations is represented by the improved Lennard-Jones expression optimized on high level ab initio energies. The weakness of the existing interaction between helium and Cs+ in comparison with some other alkali ions such as Li+ is found to play a crucial role. Our theoretical findings confirm that the first solvation layer is completed at N = 17 and both evaporation and second difference energies obtained with the PIMC calculation seem to reproduce a feature observed at N = 12 for the experimental ion abundance. The analysis of the DMC probability distributions reveals the important contribution from the icosahedral structure to the overall configuration for He12Cs+.

Published
2019

8. Snowball formation for Cs+ solvation in molecular hydrogen and deuterium

Author

Ministerio de Economía y Competitividad (España), Agencia Estatal de Investigación (España), Consejo Superior de Investigaciones Científicas (España), Austrian Science Fund, Centro de Supercomputación de Galicia, European Commission, Bartolomei, Massimiliano [0000-0001-8643-4106], González-Lezana, Tomás [0000-0003-0010-5219], Campos-Martínez, José [0000-0002-8848-6353], Hernández, Marta I. [0000-0003-3963-4345], Pérez de Tudela, Ricardo [0000-0002-0314-6983], Hernández-Rojas, Javier [0000-0003-0610-660X], Bretón, José [0000-0003-2637-2876], Pirani, F. [0000-0003-3110-6521], Scheier, Paul [0000-0002-7480-6205], Ortiz de Zárate, J., Bartolomei, Massimiliano, González-Lezana, Tomás, Campos-Martínez, José, Hernández, Marta I., Pérez de Tudela, Ricardo, Hernández-Rojas, Javier, Bretón, José, Pirani, F., Kranabetter, Lorenz, Martini, Paul, Kuhn, Martin, Laimer, Felix, Scheier, Paul, Ministerio de Economía y Competitividad (España), Agencia Estatal de Investigación (España), Consejo Superior de Investigaciones Científicas (España), Austrian Science Fund, Centro de Supercomputación de Galicia, European Commission, Bartolomei, Massimiliano [0000-0001-8643-4106], González-Lezana, Tomás [0000-0003-0010-5219], Campos-Martínez, José [0000-0002-8848-6353], Hernández, Marta I. [0000-0003-3963-4345], Pérez de Tudela, Ricardo [0000-0002-0314-6983], Hernández-Rojas, Javier [0000-0003-0610-660X], Bretón, José [0000-0003-2637-2876], Pirani, F. [0000-0003-3110-6521], Scheier, Paul [0000-0002-7480-6205], Ortiz de Zárate, J., Bartolomei, Massimiliano, González-Lezana, Tomás, Campos-Martínez, José, Hernández, Marta I., Pérez de Tudela, Ricardo, Hernández-Rojas, Javier, Bretón, José, Pirani, F., Kranabetter, Lorenz, Martini, Paul, Kuhn, Martin, Laimer, Felix, and Scheier, Paul

Abstract

Interactions of atomic cations with molecular hydrogen are of interest for a wide range of applications in hydrogen technologies. These interactions are fairly strong despite being non-covalent, hence one can ask whether hydrogen molecules would form dense, solid-like, solvation shells around the ion (snowballs) or rather a more weakly bound compound. In this work, the interactions between Cs+ and H2 are studied both experimentally and computationally. Isotopic substitution of H2 by D2 is also investigated. On the one hand, helium nanodroplets doped with cesium and hydrogen or deuterium are ionized by electron impact and the (H2/D2)nCs+ (up to n = 30) clusters formed are identified via mass spectrometry. On the other hand, a new analytical potential energy surface, based on ab initio calculations, is developed and used to study cluster energies and structures by means of classical and quantum-mechanical Monte Carlo methods. The most salient features of the measured ion abundances are remarkably mimicked by the computed evaporation energies, particularly for the clusters composed of deuterium. This result supports the reliability of the present potential energy surface and allows us to recommend its use in related systems. Clusters with either twelve H2 or D2 molecules stand out for their stability and quasi-rigid icosahedral structures. However, the first solvation shell involves thirteen or fourteen molecules for hydrogenated or deuterated clusters, respectively. This shell retains its internal structure when extra molecules are added to the second shell and is nearly solid-like, especially for the deuterated clusters. The role played by three-body induction interactions as well as the rotational degrees of freedom is analyzed and they are found to be significant (up to 15% and 18%, respectively) for the molecules belonging to the first solvation shell.

Published
2019

9. N2+(2Σg) and Rb(2S) in a hybrid trap: modeling ion losses from radiative association paths

Author

Pablo Villarreal, Ersin Yurtsever, Tomás González-Lezana, A. D. Dörfler, Stefan Willitsch, F. A. Gianturco, Yurtsever, İsmail Ersin (ORCID 0000-0001-9245-9596 & YÖK ID 7129), Gianturco, F. A., Dorfler, A. D., Willitsch, S., Gonzalez-Lezana, T., Villarreal, P., College of Sciences, Department of Chemistry, Ministerio de Ciencia e Innovación (España), Ministerio de Economía, Industria y Competitividad (España), Swiss National Science Foundation, European Commission, Consejo Superior de Investigaciones Científicas (España), Yurtsever, E., González-Lezana, Tomás, Villarreal, Pablo, Willitsch, S. [0000-0002-8376-0579], Yurtsever, E. [0000-0001-9245-9596], González-Lezana, Tomás [0000-0003-0010-5219], and Villarreal, Pablo [0000-0003-4710-9268]

Subjects
Physics, Exothermic reaction, Orders of magnitude (temperature), Ultracold molecules, Polarizabilities, Predissociation, Approximation, Ab initio, General Physics and Astronomy, 02 engineering and technology, 010402 general chemistry, 021001 nanoscience & nanotechnology, 01 natural sciences, Molecular physics, 0104 chemical sciences, Ion, Trap (computing), Reaction rate, Radiative transfer, Physical and Theoretical Chemistry, 0210 nano-technology, Chemistry, Direct process
Abstract

10 pags., 8 figs., 2 tabs. -- Open Access funded by Creative Commons Atribution Licence 3.0, By employing ab initio computed intermolecular potential energy surfaces we calculate the radiative association probabilities and rates for two different associative mechanisms involving trapped molecular ions N2 +(2Sg) interacting either directly with ultracold Rb atoms or undergoing charge-exchange (CE) processes leading to the formation of complexes of the strongly exothermic products N2(X1Sg) plus Rb+(1S0). The two processes are expected to provide possible paths to ion losses in the trap within the timescale of experiments. The present calculations suggest that the associative rates for the ‘vibrational’ direct process are too small to be of any significant importance at the millikelvin temperatures considered in the experiments, while the ‘vibronic’ path into radiatively associating the CE products has a probability of occurring which is several orders of magnitude larger. However the reaction rate constants attributed to non-adiabatic CE [F. H. J. Hall and S. Willist, Phys. Rev. Lett., 2012, 109, 233202] are in turn several orders of magnitude larger than the radiative ones calculated here, thereby making the primary experimental process substantially unaffected by the radiative losses channel., The participating groups in Innsbruck and Basel gratefully acknowledge the Marie-Curie Initial Training Network ‘‘COMIQ: Cold Molecular Ions at the Quantum limit’’ for providing financial support for the present collaboration when this work was started. TGL and PV acknowledge MICINN Grants no. FIS2014-51993-P and FIS2017-83157-P. SW acknowledges support from the Swiss National Science Foundation under grant no. 200020-175533., We acknowledge support of the publication fee by the CSIC Open Access Support Initiative through its Unit of Information Resources for Research (URICI)

Published
2019
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10. Complexes of Alkali Metal Cations and Molecular Hydrogen: Potential Energy Surfaces and Bound States

Author

Tomás González-Lezana, Fernando Pirani, Massimiliano Bartolomei, Marta I. Hernández, José Campos-Martínez, Ministerio de Economía y Competitividad (España), Ministero dell'Istruzione, dell'Università e della Ricerca, Università degli Studi di Perugia, Centro de Supercomputación de Galicia, Bartolomei, Massimiliano [0000-0001-8643-4106], González-Lezana, Tomás [0000-0003-0010-5219], Campos-Martínez, José [0000-0002-8848-6353], Hernández, Marta I. [0000-0003-3963-4345], Pirani, Fernándo [0000-0003-3110-6521], Bartolomei, Massimiliano, González-Lezana, Tomás, Campos-Martínez, José, Hernández, Marta I., and Pirani, Fernándo

Subjects
Astrochemistry, 010304 chemical physics, Chemistry, Rotational–vibrational spectroscopy, 010402 general chemistry, Alkali metal, 01 natural sciences, Potential energy, 0104 chemical sciences, Metal, Hydrogen storage, Ab initio quantum chemistry methods, visual_art, 0103 physical sciences, Bound state, Physics::Atomic and Molecular Clusters, visual_art.visual_art_medium, Physical chemistry, Physics::Chemical Physics, Physical and Theoretical Chemistry
Abstract

9 pags., 4 figs., 3 tabs., Complexes between metal cations and molecular hydrogen are systems quite amenable for precise spectroscopic and theoretical studies, and at the same time, they are relevant for applications in hydrogen storage and astrochemistry. In this work, we report new intermolecular potential energy surfaces and rovibrational states calculations for complexes involving molecular hydrogen and alkaline metal cations, M+−H2 (M+ = Na+, K+, Rb+, Cs+). The intermolecular potentials, formulated in an internally consistent way to emphasize differences in the properties of the systems, are represented by simple analytical expressions whose parameters have been optimized from comparison with accurate ab initio calculations. Properties of the low-lying bound statesbinding energies, frequencies, and rotational constantsare compared with previous measurements or computations and an overall good agreement is achieved, supporting the reliability of the present formulation. Variations of these properties as a function of the cation size and isotopic substitution, with a proper sequence of ortho and para rotational levels, are also discussed., The work has been funded by Spanish MINECO Grants FIS2017-84391-C2-2-P and FIS2017-83157-P. F.P. thanks the MIUR and the Universita degli Studi di Perugia for financial support to the project AMIS, through the program Dipartimenti di Eccellenza 2018−2022. Allocation of computing time by CESGA (Spain) is also acknowledged

Published
2019

11. A combined experimental and theoretical investigation of Cs+ ions solvated in HeN clusters

Author

Marta I. Hernández, Paul Scheier, José Luis Bretón, Javier Hernández-Rojas, Massimiliano Bartolomei, Josu Ortiz de Zárate, Marcelo Goulart, Tomás González-Lezana, Paul Martini, José Campos-Martínez, Pablo Villarreal, Ricardo Pérez de Tudela, Fernando Pirani, Austrian Science Fund, European Commission, Ministerio de Industria y Competitividad (España), Pérez de Tudela, Ricardo [0000-0002-0314-6983], Scheier, Paul [0000-0002-7480-6205], Pirani, F. [0000-0003-3110-6521], Hernández-Rojas, Javier [0000-0003-0610-660X], Bretón, José [0000-0003-2637-2876], Bartolomei, Massimiliano [0000-0001-8643-4106], González-Lezana, Tomás [0000-0003-0010-5219], Hernández, Marta I. [0000-0003-3963-4345], Campos-Martínez, José [0000-0002-8848-6353], Villarreal, Pablo [0000-0003-4710-9268], Pérez de Tudela, Ricardo, Scheier, Paul, Pirani, F., Hernández-Rojas, Javier, Bretón, José, Bartolomei, Massimiliano, González-Lezana, Tomás, Hernández, Marta I., Campos-Martínez, José, and Villarreal, Pablo

Subjects
Materials science, 010304 chemical physics, Monte Carlo method, Ion-helium clusters, Ab initio, Solvation, General Physics and Astronomy, Monte Carlo methods, 010402 general chemistry, 01 natural sciences, Molecular physics, Ion-helium clusters, mass spectra, Monte Carlo methods, mass spectra, 3. Good health, 0104 chemical sciences, Ion, Solvation shell, Ab initio quantum chemistry methods, 0103 physical sciences, Physics::Atomic and Molecular Clusters, Diffusion Monte Carlo, Physical and Theoretical Chemistry, Path integral Monte Carlo
Abstract

11 pags., 13 figs., Solvation of Cs+ ions inside helium droplets has been investigated both experimentally and theoretically. On the one hand, mass spectra of doped helium clusters ionized with a crossed electron beam, HeNCs+, have been recorded for sizes up to N = 60. The analysis of the ratio between the observed peaks for each size N reveals evidences of the closure of the first solvation shell when 17 He atoms surround the alkali ion. On the other hand, we have obtained energies and geometrical structures of the title clusters by means of basin-hopping, diffusion Monte Carlo (DMC), and path integral Monte Carlo (PIMC) methods. The analytical He–Cs+ interaction potential employed in our calculations is represented by the improved Lennard-Jones expression optimized on high level ab initio energies. The weakness of the existing interaction between helium and Cs+ in comparison with some other alkali ions such as Li+ is found to play a crucial role. Our theoretical findings confirm that the first solvation layer is completed at N = 17 and both evaporation and second difference energies obtained with the PIMC calculation seem to reproduce a feature observed at N = 12 for the experimental ion abundance. The analysis of the DMC probability distributions reveals the important contribution from the icosahedral structure to the overall configuration for He12Cs+., This work was supported by the Austrian Science Fund, FWF (Project Nos. P23657 and P31149); the European Commission (ELEvaTE H2020 Twinning Project, Project No. 692335); and the MINECO with Grant Nos. FIS2014-51993-P, FIS2016-79596-P, FIS2017-84391-C2-2-P, and FIS2017-83157-P.

Published
2019

12. Snowball formation for Cs+ solvation in molecular hydrogen and deuterium

Author

Fernando Pirani, Ricardo Pérez de Tudela, Massimiliano Bartolomei, José Campos-Martínez, Felix Laimer, Javier Hernández-Rojas, Paul Martini, Martin Kuhn, Lorenz Kranabetter, Josu Ortiz de Zárate, Paul Scheier, Tomás González-Lezana, José Luis Bretón, Marta I. Hernández, Ministerio de Economía y Competitividad (España), Agencia Estatal de Investigación (España), Consejo Superior de Investigaciones Científicas (España), Austrian Science Fund, Centro de Supercomputación de Galicia, European Commission, Bartolomei, Massimiliano [0000-0001-8643-4106], González-Lezana, Tomás [0000-0003-0010-5219], Campos-Martínez, José [0000-0002-8848-6353], Hernández, Marta I. [0000-0003-3963-4345], Pérez de Tudela, Ricardo [0000-0002-0314-6983], Hernández-Rojas, Javier [0000-0003-0610-660X], Bretón, José [0000-0003-2637-2876], Pirani, F. [0000-0003-3110-6521], Scheier, Paul [0000-0002-7480-6205], Bartolomei, Massimiliano, González-Lezana, Tomás, Campos-Martínez, José, Hernández, Marta I., Pérez de Tudela, Ricardo, Hernández-Rojas, Javier, Bretón, José, Pirani, F., and Scheier, Paul

Subjects
Materials science, Hydrogen, Solvation, General Physics and Astronomy, chemistry.chemical_element, 02 engineering and technology, 010402 general chemistry, 021001 nanoscience & nanotechnology, 01 natural sciences, 0104 chemical sciences, Ion, Cation-hydrogen clusters, Cation-hydrogen clusters, helium nanodroplets, mass spectrometry, classical and quantum-mechanical Monte Carlo methods, Solvation shell, Deuterium, chemistry, Chemical physics, Ab initio quantum chemistry methods, helium nanodroplets, Potential energy surface, Molecule, Physical and Theoretical Chemistry, classical and quantum-mechanical Monte Carlo methods, 0210 nano-technology, mass spectrometry
Abstract

7 pags., 5 figs. -- Open Access funded by Creative Commons Atribution Licence 3.0, Interactions of atomic cations with molecular hydrogen are of interest for a wide range of applications in hydrogen technologies. These interactions are fairly strong despite being non-covalent, hence one can ask whether hydrogen molecules would form dense, solid-like, solvation shells around the ion (snowballs) or rather a more weakly bound compound. In this work, the interactions between Cs+ and H2 are studied both experimentally and computationally. Isotopic substitution of H2 by D2 is also investigated. On the one hand, helium nanodroplets doped with cesium and hydrogen or deuterium are ionized by electron impact and the (H2/D2)nCs+ (up to n = 30) clusters formed are identified via mass spectrometry. On the other hand, a new analytical potential energy surface, based on ab initio calculations, is developed and used to study cluster energies and structures by means of classical and quantum-mechanical Monte Carlo methods. The most salient features of the measured ion abundances are remarkably mimicked by the computed evaporation energies, particularly for the clusters composed of deuterium. This result supports the reliability of the present potential energy surface and allows us to recommend its use in related systems. Clusters with either twelve H2 or D2 molecules stand out for their stability and quasi-rigid icosahedral structures. However, the first solvation shell involves thirteen or fourteen molecules for hydrogenated or deuterated clusters, respectively. This shell retains its internal structure when extra molecules are added to the second shell and is nearly solid-like, especially for the deuterated clusters. The role played by three-body induction interactions as well as the rotational degrees of freedom is analyzed and they are found to be significant (up to 15% and 18%, respectively) for the molecules belonging to the first solvation shell., work has been funded by Spanish MINECO grants (FIS2014-51993-P, FIS2016-79596-P, FIS2017-84391-C2-2-P and FIS2017-83157-P) and by the Austrian Science Fund, Wien (FWF Projects P26635, P31149, and W1259). Allocation of computing time by the CESGA (Spain) is also acknowledged. JOZ would like to acknowledge Programa Operativo de Empleo Juvenil 2014-2020 from the European Social Fund., We acknowledge support of the publication fee by the CSIC Open Access Support Initiative through its Unit of Information Resources for Research (URICI)

Published
2019

13. Vibrational predissociation dynamics of the He79Br2van der Waals molecule: A quantum mechanical study

Author

Gerardo Delgado-Barrio, Tomás González-Lezana, Marta I. Hernández, Alexei A. Buchachenko, Pablo Villarreal, Dirección General de Investigación Científica y Técnica, DGICT (España), European Commission, González-Lezana, Tomás, Hernández, Marta I., Delgado Barrio, Gerardo, Buchachenko, Alexei A., Villarreal, Pablo, González-Lezana, Tomás [0000-0003-0010-5219], Hernández, Marta I. [0000-0003-3963-4345], Delgado Barrio, Gerardo [0000-0002-8289-1366], Buchachenko, Alexei A. [0000-0003-0701-5531], and Villarreal, Pablo [0000-0003-4710-9268]

Subjects
Chemistry, Van der Waals molecule, Binding energy, General Physics and Astronomy, Bromine complexes, Dissociation (chemistry), symbols.namesake, Fragmentation (mass spectrometry), Physics::Atomic and Molecular Clusters, symbols, Physical and Theoretical Chemistry, Atomic physics, van der Waals force, Quantum
Abstract

10 pags., 5 figs., 4 tabs., The vibrational predissociation of the HeBr2 van der Waals complex is studied by means of both accurate and approximate three dimensional quantum mechanical calculations. Simple atom–atom potentials have been tested for matching experimental measurements at low Br2 vibrational excitations. The fragmentation dynamics when the bromine subunit is close to its B state dissociation limit is then explored and compared with experiments. For low to intermediate vibrational states v, good agreement with most of the data (spectral shifts, lifetimes, average structures, average product energies) is achieved. The closing of the Δv=−1 channel at v=44 and the binding energy at that position are successfully reproduced, although calculated and experimental blueshifts and linewidths are not in such good accordance in the v≳38 range. For these high v excitations, fragmentation cross sections exhibit complicated structures indicating strong interactions among different quasibound states. In addition, interesting threshold and intramolecular energy redistribution effects are predicted. The closing of the Δv=−1 channel is found to be a gradual process where different dynamical regimes can be investigated in detail., This work has been supported by the D.G.I.C.Y.T. Grant PB95-0071 (Spain), and the INTAS-93- 1809 and CI1*-CT94-0128 Grants (European Union).

Published
1996
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