Time-dependent configuration-interaction-singles calculation of the 5 p-subshell two-photon ionization cross section in xenon

The 5p two-photon ionization cross section of xenon in the photon-energy range below the one-photon ionization threshold is calculated within the time-dependent configuration-interaction-singles (TDCIS) method. The TDCIS calculations are compared to random-phase-approximation calculations [Wendin et al., J. Opt. Soc. Am. B 4, 833 (1987)] and are found to reproduce the energy positions of the intermediate Rydberg states reasonably well. The effect of interchannel coupling is also investigated and found to change the cross section of the 5p shell only slightly compared to the intrachannel case.