Photoionization of excited-state xenon

The photoionization cross section of Xe 5p⁵²P3/26p(J=0) is calculated near threshold. We use a jjJM-coupling scheme to describe the excited-state spectrum of xenon. By transformation from jj to LS coupling, one set of cross-section results is obtained using bound and continuum orbitals generated in the Hartree-Fock approximation. Another set of cross-section results is obtained using orbitals generated in the Dirac-Fock approximation. The difference in the two sets of results, which represents the contribution from relativistic effects, is found to be as much as 25% at certain energies. On the other hand, differences in the cross-section results which arise from the choice of electromagnetic field gauge are found to be as much as 75%.