Comparison of calculated PI cross sections (solid lines) with experimental data (dotted lines) for Kr⁰ (Richter et al. 2003), Kr³⁺ (Lu et al. 2006b), Kr⁴⁺ (Lu 2006), and Kr⁵⁺ (Lu et al. 2006a). The theoretical curves have been convolved with a Gaussian of 1 eV for Kr⁰ and 100 meV for the other species, to match the experimental resolution. The theoretical data are linear combinations of PI cross sections from each state in the ground configuration, weighted according to statistical weights in the case of Kr³⁺, and by the factors (³P₀, ³P₁, ³P₂, ¹D₂, ¹S₀) = (0.32, 0.15, 0.2, 0.3, 0.03) for Kr⁴⁺ and (²P_1/2, ²P_3/2) = (0.4, 0.6) for Kr⁵⁺.