Double-slit, confinement, and non-Franck-Condon effects in photoionization of H_2 at high photon energy

摘要

A detailed theoretical study of H2 ionization by photons of a few hundreds of eV is presented. Bound and continuum states are accurately evaluated by using B-spline basis functions. The nuclear degrees of freedom are also included. A striking feature is observed when one analyzes .the vibrational distribution of the residual H_2~ + ion: this vibrational distribution does not follow the usual Franck-Condon behavior when H_2 is parallel to the polarization direction. The origin of this anomaly is related to interference effects. Such effects are more clearly seen in the fully differential electron angular distributions associated with specific vibrational states of H_ 2~ +: for H_2 molecules perpendicular to the polarization direction, the distributions clearly resemble those obtained in Young's double-slit experiment, while, for molecules parallel to the polarization direction, they show that the electron is sometimes prevented to escape in the direction of the radiation field due to the suppression (or confinement) of a given partial wave. The calculations also show that, at these high photon energies, the nuclear asymmetry parameter exhibits a reminiscence of Cohen-Fano oscillations when it is plotted as a function of photon energy.