Infrared spectral fingerprint of neutral and charged endo- and exohedral metallofullerenes

Small metal-containing molecules have been detected and recognized as one of the hybrid species efficiently formed in space; especially in the circumstellar envelopes of evolved stars. It has been predicted also that more complex hybrid species like those formed by metals and fullerenes (metallofullerenes) could be present in such circumstellar environments. Recently, quantum-chemical simulations of metallofullerenes have shown that they are potential emitters contributing to the observed mid-IR spectra in the fullerene-rich circumstellar environments of different types of evolved stars. Here we present the individual simulated mid-IR (~5-50 um) spectra of twenty-eight metallofullerene species; both neutral and charged endo- and exohedral metallofullerenes for seven different metals (Li, Na, K, Ca, Mg, Ti, and Fe) have been considered. The changes induced by the metal-C60 interaction on the intensity and position of the spectral features are highlighted using charge density difference maps and electron density partitioning. Our calculations identify the fundamental IR spectral regions where, depending on the metal binding nature, there should be a major spectral contribution from each of the metallofullerenes. The metallofullerenes IR spectra are made publicly available to the astronomical community, especially James Webb Space Telescope users, for comparisons that could eventually lead to the detection of these species in space.Comment: Accepted for publication in The Astrophysical Journal Supplement Series on 19 September 2023 (in press) (13 pages, 7 figures, and 1 table

Decay pathways for protonated and deprotonated adenine molecules

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Journal of Chemical Physics 151.4 (2019): 044306 and may be found at https://aip.scitation.org/doi/abs/10.1063/1.5109963We have measured fragment mass spectra and total destruction cross sections for protonated and deprotonated adenine following collisions with He at center-of-mass energies in the 20-240 eV range. Classical and ab initio molecular dynamics simulations are used to provide detailed information on the fragmentation pathways and suggest a range of alternative routes compared to those reported in earlier studies. These new pathways involve, for instance, losses of HNC molecules from protonated adenine and losses of NH2 or C3H2N2 from deprotonated adenine. The present results may be important to advance the understanding of how biomolecules may be formed and processed in various astrophysical environmentsThis work was supported by the Swedish Research Council (Constant Nos. 2017-00621, 2015-04990, 2016-04181, and 2018-04092). Furthermore, we acknowledge the European Joint on Theoretical Chemistry and Computational Modelling (INT-EJD-TCCM). We acknowledge the generous allocation of computer time at the Centro de Computacion Cientifica at the Universidad Autonoma de Madrid (CCC-UAM). This work was partially supported by Project No. CTQ2016-76061-P of the Spanish Ministerio de Economia y Competitividad (MINECO

Theoretical study of electron confinement in Cu corrals on a Cu(111) surface

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Electron propagation along Cu nanowires supported on a Cu(111) surface.

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Fragmentation of hydrocarbons by collision. AGAT@ANDROMEDE.

International audienceWe are studying small hydrocarbons produced in high velocity (3.4 a.u.) collision between ${{\rm{CH}}}_{y}^{+}$ cations and He atoms. During the collision those hydrocarbons gain some energy and release this energy doing fragmentation. Thanks to the detector AGAT we have been able to measure fragmentation branching ratios for ${{\rm{CH}}}_{y}^{q+}$ (y=2-4, q=0-3). We also constructed semi-empirical breakdown curves for ${{\rm{CH}}}_{y}^{q+}$ using these experimental branching ratios

Energy deposit by electron excitation in C_nN⁺ projectiles (n=1-3) colliding at in termediate velocity with He atoms : semi-empirical estimates and calculations

International audienceSynopsis Using measured dissociation branching ratios and theoretical dissociation energies, we extracted semi-empirical estimates of the energy deposit due to electron excitation in CnN+-He collisions at v=2.2 a.u. We compared these estimates to calculations based on the IAE (Independent Atom and Electron) model where the atom(ion)-atom excitation is treated within the Classical Trajectory Monte Carlo (CTMC) approach. A good agreement has been found. This atomic approach is also able to reproduce the experimental Kinetic Energy Release (KER) in CN+ dissociation measured in 3.5 a.u CN+-He collision.</jats:p