Open AccessSignatures of attosecond electronic–nuclear dynamics in the one-photon ionization of molecular hydrogen: analytical model versusab initiocalculations
Author(s) -
Lukas Medišauskas,
Felipe Morales,
Alicia Palacios,
Alberto González-Castrillo,
L. I. Plimak,
Olga Smirnova,
Fernando Martı́n,
Misha Ivanov
Publication year - 2015
Publication title -
new journal of physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.584
H-Index - 190
ISSN - 1367-2630
DOI - 10.1088/1367-2630/17/5/053011
Subject(s) - autoionization , physics , atomic physics , photoionization , wave packet , wkb approximation , attosecond , ionization , ab initio , ab initio quantum chemistry methods , ground state , electronic structure , excited state , wave function , dissociation (chemistry) , photon , quantum mechanics , molecule , laser , ion , chemistry , ultrashort pulse
We present an analytical model based on the time-dependent WKB approximation to reproduce the photoionization spectra of an H2 molecule in the autoionization region. We explore the nondissociative channel, which is the major contribution after one-photon absorption, and we focus on the features arising in the energy differential spectra due to the interference between the direct and the autoionization pathways. These features depend on both the timescale of the electronic decay of the autoionizing state and the time evolution of the vibrational wavepacket created in this state. With full ab initio calculations and with a one-dimensional approach that only takes into account the nuclear wavepacket associated to the few relevant electronic states we compare the ground state, the autoionizing state, and the background continuum electronic states. Finally, we illustrate how these features transform from molecular-like to atomic-like by increasing the mass of the system, thus making the electronic decay time shorter than the nuclear wavepacket motion associated with the resonant state. In other words, autoionization then occurs faster than the molecular dissociation into neutralsWe acknowledge computer time from the CCC-UAM and Mare Nostrum supercomputer centers and financial support by the European Research Council under the ERC Advanced Grant no. 290853 XCHEM, FP7 Marie Curie ITN CORINF, FP7 Marie Curie IRG ATTOTREND, the Ministerio de Economía y Competitividad projects FIS2010-15127, FIS2013-42002 R and ERA-Chemistry PIM2010EEC-00751, the European COST Action CM1204 XLIC, and EPSRC programme no. EP/I032517/