Abstract

In this work, we present the photon energy dependence of the two- and three-photon cross sections of the two-electron Li⁺, Ne⁸⁺ and Ar¹⁶⁺ ions, following photoionization from their ground state. The expressions for the cross sections are based on the lowest-order (non-vanishing) perturbation theory for the electric field, while the calculations are made with the use of an ab initio configuration interaction method. The ionization cross section is dominated by pronounced single photon resonances in addition to peaks associated with doubly excited resonances. In the case of two-photon ionization, and in the non-resonant part of the cross section, we find that the ¹D ionization channel overwhelms the ¹S one. We also observe that, as one moves from the lowest atomic number ion, namely Li⁺, to the highest atomic number ion, namely Ar¹⁶⁺, the cross sections generally decrease. View Full-Text