title: Autoionization of molecular hydrogen: where do the Fano lineshapes go?
abstract: Atomic autoionization following photoabsorption is a typical example of quantum interferences governed by electron-electron correlation. Coherence between direct photoionization and autoionization paths results in "Fano profiles", widely explored in atoms in the last 60 years. The advent of femto- and attosecond laser technology made time-resolved images of the delayed electron ejection in autoionization accessible, leading to the reemergence of such studies in atomic systems. The counterpart molecular phenomena show the richness, as well as the complexity, added by nuclear motion, which may proceed on similar time scales. However, Fano profiles are usually absent in measured molecular photoionization cross sections and an unequivocal parametrization of molecular autoionization signatures, similar to that introduced by Fano in atoms [U. Fano, Phys. Rev. 1961, 124, 1866] has not yet been achieved. In this work we introduce a simple semiclassical model that accounts for all the features observed in H2 photoionization and demonstrate that the interference structures observed in dissociative ionization spectra are almost exclusively due to the phase accumulated in the nuclear motion. Furthermore, we show that the temporal build-up of these structures in the energy-differential cross sections is also determined by nuclear motion. We validate our models by comparing with full-dimensional ab initio calculations solving the time-dependent Schrödinger equation.
authors.affiliation: Departamento de Química, Modulo 13, Universidad Autónoma de Madrid, 28049 Madrid, Spain. alicia.palacios@uam.es
authors.forename: Alicia
authors.initials: A
authors.lastname: Palacios
authors.forename: Johannes
authors.initials: J
authors.lastname: Feist
authors.forename: Alberto
authors.initials: A
authors.lastname: González-Castrillo
authors.forename: José Luis
authors.initials: JL
authors.lastname: Sanz-Vicario
authors.forename: Fernando
authors.initials: F
authors.lastname: Martín
mesh_terms: D006859:Hydrogen / Q000737:chemistry*; D007700:Kinetics; D011789:Quantum Theory; D013997:Time Factors
chemical_list: D006859:Hydrogen