Two-photon double ionization of He and H⁻

Abstract

Two-photon absorption processes resulting in two-electron ionization of He and H − are calculated using a time-dependent close-coupling expansion on a two-dimensional radial lattice. The ground state atom or ion is subjected to a 10-cycle pulse of linearly polarized light with peak intensities ranging from 10 13 to 10 16 W cm −2 . Probabilities are calculated for one-photon single ionization, two-photon single ionization and two-photon double ionization. The ratio of non-sequential double ionization to single ionization following two-photon absorption is found to be somewhat larger than the similar ratio following one-photon absorption.