Photoionization and electron-impact ionization ofKr3+

Abstract

Absolute photoionization cross sections for ${\mathrm{Kr}}^{3+}$ were measured in the energy range $39.05--143.2\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ for single ionization and $120.6--137.7\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ for double ionization. For comparison, an electron-impact single-ionization measurement was made in the energy range $43.1--179.1\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ and normalized to previously published absolute measurements. The Flexible Atomic Code and Cowan atomic structure codes were used to calculate energy levels, excitation energies and oscillator strengths for $3d\ensuremath{\rightarrow}np$, $3d\ensuremath{\rightarrow}nf$, and $4s\ensuremath{\rightarrow}np$ autoionizing transitions from the ground and metastable states. From the single-photoionization measurements, ionization thresholds of the $^{2}P^{o}_{3∕2}$, $^{2}D^{o}_{5∕2}$ metastable states and $^{4}S^{o}_{3∕2}$ ground state were measured to be $46.62\ifmmode\pm\else\textpm\fi{}0.02$, $48.59\ifmmode\pm\else\textpm\fi{}0.01$, and $50.70\ifmmode\pm\else\textpm\fi{}0.02\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$, nearly $2\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ lower than National Institute of Standards and Technology tabulated values. Within the experimental uncertainty, oscillator strengths determined from the photoionization measurements are in agreement with both calculations. Excitation-autoionization and resonant-excitation double-autoionization features are evident in the electron-impact ionization cross section.