Near-threshold photoionization of the Xe 3d spin-orbit doublet: Relativistic, relaxation, and intershell interaction effects

Results of calculations of the near-threshold photoionization of the xenon 3d spin-orbit doublet are reported. Our theoretical analysis is undertaken in order to interpret and enlighten the very detailed measurements of this process [A. Kivimäki et al., Phys. Rev. A 63, 012716 (2001)], which revealed a previously unobserved interesting feature—an additional broad maximum—in the partial xenon 3d_5/2 cross section. This double maximum was not produced by earlier calculations, except in the recent study by Amusia et al. [Phys. Rev. Lett. 88, 093002 (2002)], which, in contrast to the present one, is not ab initio and relativistic in character. The partial photoionization cross sections of 3d_5/2 and 3d_3/2 subshells, photoelectron anisotropy parameters, and spin-polarization parameters that were so far not studied either experimentally or theoretically are calculated. Many-electron correlations, relativistic effects, and relaxation effects of the ionic core in the ionization process are taken into account by using the relativistic random-phase approximation, modified to include the relaxation of the considered subshell.