Photoionization of excited-state xenon

The photoionization cross section of Xe $5p^5{}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}6p(J=0\mathrm{})\mathrm{}$ is calculated near threshold. We use a $\mathrm{jjJM}$-coupling scheme to describe the excited-state spectrum of xenon. By transformation from $\mathrm{jj}$ to $\mathrm{LS}$ 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%.