Vibrationally resolved cross sections for single-photon ionization of LiH

Abstract

Ab initio studies of the single-photon ionization of LiH(X 1Σ+) leading to LiH+(X 2Σ+) are reported. The process is studied as function of the internuclear distance (2 a.u.–6 a.u.) and the kinetic energy of the electron (0.05 eV–10 eV). The calculations are based on the so-called iterative Schwinger approach which is implemented within the frozen-core single center approximation. By comparing vibrationally resolved cross sections calculated beyond and within the Franck–Condon principle we find, that the Franck–Condon principle applies relatively well to the present photoionization process. The vibrational wave functions needed for these calculations are obtained from very accurate CI-potentials, also reported in this paper. For LiH the first 10 vibrational spacings are found to agree with the experimental data within 0.2%. Photoelectron spectra (PES) calculated under simulated experimental conditions suggest that photoionization experiments on LiH may yield information on the vibrational structure of LiH+. The calculated permanent dipole moment of the LiH ground state shows strong influence of the ion-pair channel (Li+H−).