Partial cross sections and angular-distribution asymmetry parameters were measured for subshell photoionization of xenon for photon energies between 40 and 1000 eV. These large-scale measurements show that the pronounced interchannel coupling between the valence and the 4d electrons persists beyond the 4d shape resonance in the subsequent Cooper-minimum region. Multielectron processes associated with 4d and 4p photoemission were measured directly for the first time over a broader energy range covering the near-threshold behavior up to the sudden limit. Comparing our experimental results with calculations based on the single-particle model shows that this theory, which fails to describe the intermediate energy range even qualitatively for the valence electrons, gives partial cross sections in reasonable agreement with experiment at higher photon energies, particularly beyond the 3d threshold. The same result is shown by the angular-distribution asymmetry parameter P, except for the photoionization of the "4p" subshell which resembles more the behavior of a 4d electron, corroborating the theoretical assumptions of core-hole fluctuations between these two subshells. In the shape resonance region the presented 4d partial cross sections are in reasonable agreement with theoretical results obtained recently by many-body perturbation theory.

Electron spectroscopy, combined with synchrotron radiation in the photon-energy range hv=60 -190 eV, was used to measure the angular distributions of Xe 5p and 5s photoelectrons and of N4 500 Auger electrons. The branching ratios and partial cross sections for photoionization and Auger processes were also measured in certain cases. The measured asymmetry parameter P for Sp photoelectrons agrees well with many-electron calculations, which predict a pronounced oscillation in P5p above the 4d ionization threshold due to the 4d-5p intershell interaction. The N4 qOO Auger electrons are produced with photon-energy-dependent anisotropic angular distributions, resulting from alignment of Xe by photoionization. The theoretical analysis of Auger-electron angular distributions is described, and theoretical calculations are found to predict the measured asymmetries well. In addition, Auger-electron peaks were observed to broaden and shift at photon energies near the 4d ionization threshold because of postcollision interaction. The measured shifts of the N~0 lO' So line agree with previous measurements and theory. Electron spectra recorded through the energy region of the 4d~np Rydberg states show that they decay primarily by the Auger process, while the 5p and 5s partial cross sections are relatively weakly affected by autoionization. However, distinct resonance structure was observed in the P parameters for Sp3/2 and Sp~q2 photoelectrons. The measured results are compared with a theoretical calculation of resonant photoionization for the 4d~6p excitation.

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Partial photoionization cross sections and angular-distribution asymmetry parameters were determined for Kr 3d photoemission using photon energies of 100 to 280 eV (to 800 eV for the asymmetry parameter). For the 3p subshell, the branching ratio relative to the 3d cross section and the asymmetry parameter were measured using energies of 280 to 800 eV. These results show good agreement with Hartree-Fock-theory predictions at all photon energies. The summed intensity of 4p~np satellites relative to the 3d main line was found to be approximately constant in the photon-energy range 180 -280 eV, and the average asymmetry parameter for these shake-up states showed a marked increase over the same energy range.