Photoionization and electron-impact ionization of Kr{sup 3+}

Absolute photoionization cross sections for Kr{sup 3+} were measured in the energy range 39.05-143.2 eV for single ionization and 120.6-137.7 eV for double ionization. For comparison, an electron-impact single-ionization measurement was made in the energy range 43.1-179.1 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{yields}np, 3d{yields}nf, and 4s{yields}np autoionizing transitions from the ground and metastable states. From the single-photoionization measurements, ionization thresholds of the {sup 2}P{sup o}{sub 3/2}, {sup 2}D{sup o}{sub 5/2} metastable states and {sup 4}S{sup o}{sub 3/2} ground state were measured to be 46.62{+-}0.02, 48.59{+-}0.01, and 50.70{+-}0.02 eV, nearly 2 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.