Total and differential cross-section calculations for the double photoionization of the helium1s2s1,3Sstates

Abstract

We apply the time-dependent close-coupling method to the double photoionization of helium from its $1s2s$ ${}^{1,3}S$ metastable states. Total integral cross sections are in excellent agreement with other nonperturbative theories. Single and triple differential cross sections are also presented which show interesting differences with previous calculations from the ${1s}^{2}$ ground state of helium. This set of calculations provides a goal for experimentalists to measure absolute total and angular differential cross sections for double ionization processes from excited states of atoms.