Electron-spectroscopy study of inner-shell photoexcitation and ionization of Xe

Abstract

Electron spectroscopy, combined with synchrotron radiation in the photon-energy range $h\nu \simeq 60-190$ eV, was used to measure the angular distributions of Xe $5p$ and $5s$ photoelectrons and of $N_{4,5}\mathrm{OO}$ Auger electrons. The branching ratios and partial cross sections for photoionization and Auger processes were also measured in certain cases. The measured asymmetry parameter $\beta$ for $5p$ photoelectrons agrees well with many-electron calculations, which predict a pronounced oscillation in ${\beta }_{5p}$ above the $4d$ ionization threshold due to the $4d-5p$ intershell interaction. The $N_{4,5}\mathrm{OO}$ Auger electrons are produced with photon-energy-dependent anisotropic angular distributions, resulting from alignmentof ${\mathrm{Xe}}^{+}$ 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 $N_5{O}_1{O}_1$ ${}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$ line agree with previous measurements and theory. Electron spectra recorded through the energy region of the $4d\to \mathrm{np}$ 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 $\beta$ parameters for $5p_{\frac{3}{2}}$ and $5p_{\frac{1}{2}}$ photoelectrons. The measured results are compared with a theoretical calculation of resonant photoionization for the $4d\to 6p$ excitation.