Photoionization and electron-impact ionization ofKr3+

Absolute photoionization cross sections for ${\mathrm{Kr}}^{3+}$ were measured in the energy range $39.05–143.2\mathrm{eV}$ for single ionization and $120.6–137.7\mathrm{eV}$ for double ionization. For comparison, an electron-impact single-ionization measurement was made in the energy range $43.1–179.1\mathrm{eV}$ 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 $3d\to np$, $3d\to nf$, and $4s\to np$ 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 $46.62\pm 0.02$, $48.59\pm 0.01$, and $50.70\pm 0.02\mathrm{eV}$, nearly $2\mathrm{eV}$ 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.