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

TLDR

Electron spectroscopy with synchrotron radiation (60–190 eV) was employed to measure angular distributions, branching ratios, and partial cross sections of Xe 5p, 5s photoelectrons and N4,5OO Auger electrons, and theoretical analysis of the Auger‑electron angular distributions was performed. The measured asymmetry parameters for Xe 5p photoelectrons agree with many‑electron calculations and exhibit pronounced oscillations above the 4d threshold, while N4,5OO Auger electrons show photon‑energy‑dependent anisotropic distributions that broaden and shift near the 4d threshold due to post‑collision interaction, with theoretical predictions matching the observed asymmetries and energy shifts.

Abstract

Electron spectroscopy, combined with synchrotron radiation in the photon-energy range $h\ensuremath{\nu}\ensuremath{\simeq}60\ensuremath{-}190$ 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 $\ensuremath{\beta}$ for $5p$ photoelectrons agrees well with many-electron calculations, which predict a pronounced oscillation in ${\ensuremath{\beta}}_{5p}$ above the $4d$ ionization threshold due to the $4d\ensuremath{-}5p$ 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 $4d\ensuremath{\rightarrow}\mathrm{np}$ 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 $\ensuremath{\beta}$ parameters for $5{p}_{\frac{3}{2}}$ and $5{p}_{\frac{1}{2}}$ photoelectrons. The measured results are compared with a theoretical calculation of resonant photoionization for the $4d\ensuremath{\rightarrow}6p$ excitation.