Resonance analysis in the photoionization of excited lithium below the1s2land1s3lionization thresholds of the Li atom

Abstract

Calculations of $1s$ electron inner-shell photoionization from the ${1s}^{2}2p{}^{2}{P}^{o}$ Li excited state were previously reported using the R-matrix code [Zhou et al., Phys. Rev. A 59, 462 (1999)]. These calculations included important resonances in the partial and total photoionization cross sections for incident photon energies (i) lower than 74 eV and due to the ${1snln}^{\ensuremath{'}}{l}^{\ensuremath{'}}{}^{2}{L}^{e}$ autoionizing states for $n=2$ and 3 and $L=S,$ $P,$ and $D,$ and (ii) larger than 140 eV and due to the ${2ln}^{\ensuremath{'}}{l}^{\ensuremath{'}}{n}^{\ensuremath{''}}{l}^{\ensuremath{''}}{}^{2}{L}^{e}$ autoionizing states. The latter resonances corresponding to ${2ln}^{\ensuremath{'}}{l}^{\ensuremath{'}}{n}^{\ensuremath{''}}{l}^{\ensuremath{''}}$ were recently analyzed by Zhou et al. [Phys. Rev. A 62, 012707 (2000)], using an eigenphase derivative technique along with quantum defect theory. The present paper proposes an analysis of the former resonances in the 58--74 eV incident photon energy range. The determination of the resonant positions for each series converging to a $1s2l{}^{1,3}L$ or $1s3l{}^{1,3}L$ ionization threshold of Li is obtained using the same method as in Zhou et al. [Phys. Rev. A 62, 012707 (2000)]. The identifications are compared with theoretical results of Chung [Phys. Rev. A 57, 3518 (1998)] using the saddle-point method for energies below the ${\mathrm{Li}}^{+}1s2s{}^{1}S$ threshold. Agreement is excellent in most cases and some discrepancies are discussed.