Photoionization of the ground and first two metastable levels for Sc III: Configuration-interaction and relativistic effects

Abstract

The photoionization cross section of the ground $([\mathrm{Ne}]{3s}^{2}{3p}^{6}3d$ ${}^{2}{D}_{3/2})$ and first two metastable $([\mathrm{Ne}]{3s}^{2}{3p}^{6}3d$ ${}^{2}{D}_{5/2}$ and $[\mathrm{Ne}]{3s}^{2}{3p}^{6}4s$ ${}^{2}{S}_{1/2})$ levels of potassiumlike Sc III have been studied using fully relativistic R-matrix method. To show the effects of configuration interaction on the cross section, we first perform a nonrelativistic R-matrix calculation. The detailed structures and resonances of the cross section obtained by the fully relativistic method in the region of $3\stackrel{\ensuremath{\rightarrow}}{p}3d$ and $3\stackrel{\ensuremath{\rightarrow}}{p}4s$ resonances are described and analyzed in some detail. The positions, autoionization widths, and oscillator strengths of some prominent resonances are determined. The calculated cross section is compared with a recent experiment [S. Schippers et al., Phys. Rev. Lett. 89, 193002 (2002)]. The resonance energies and intensities predicted by the fully relativistic calculations agree well with the experiment, especially for the $3\stackrel{\ensuremath{\rightarrow}}{p}4s$ resonances in the region of lower photon energy, while it is not so satisfactory for the nonrelativistic calculations. Our results show that not only adequate configuration interaction, particularly the ${3p}^{3}\ensuremath{\rightarrow}{3d}^{3}$ core-valence correlations, but also relativistic effects should be carefully included in the calculation to obtain a good agreement with the experiment.