Photoionization of the outer shells of neon, argon, krypton, and xenon using the relativistic random-phase approximation

Multichannel photoionization calculations using the relativistic random-phase approximation for the outer shells in the rare gases, neon, argon, krypton, and xenon, are presented. Total cross sections and partial cross sections for $\mathrm{ns}$ subshells are determined and compared with experiment and with alternative calculations at low energies. Branching ratios of ${}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}:{}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}$ cross sections which are sensitive to relativistic and correlation effects are presented and compared with experiment. Angular distribution asymmetry parameters $\beta$ determined for each subshell are found and compared with experiment; the differences between $\beta$ values for ${}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}$ and ${}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}$ subshells in krypton and xenon emphasize the importance of relativistic effects in outer subshells of heavy elements. Values of $\beta$ are given for outermost $s$ electrons which show large relativistic effects near the "Cooper minima" of the corresponding partial cross sections. Eigenphases from the multichannel analysis are presented for argon to illustrate mathematical features of the present calculation.