Photoemission from Xe in the vicinity of the 4dCooper minimum

Partial photoionization cross sections and angular-distribution asymmetry parameters have been determined for the Xe 4d and ‘‘4p’’ subshells in the photon-energy region of the 4d Cooper minimum (160 eV to 270 eV, to 520 eV for the 4d asymmetry parameter). The Cooper minimum is observed as a distinct cross-section minimum in the 4d photoionization channel. The 4d angular-distribution results are in excellent agreement with Dirac-Fock and relativistic random-phase-approximation calculations and with previous measurements. Effects of interchannel coupling are evident in the ‘‘4p’’ results. Both the partial cross section and the angular distribution for the ‘‘4p’’ photoelectron peak track the 4d cross section and angular distribution as functions of photon energy. A similar result is observed for the summed intensity and the angular distribution of the 4$d^{\mathrm{-}1}$5$p^{\mathrm{-}1}$np satellites of the 4d main line, which is probably due to the effects of electron correlation between the 4d and the satellite photoionization channels.