Resonance structure in the 2p photoionization of atomic sodium close to the 2s threshold.

Abstract

We calculated 2p inner-shell photoionization cross sections of atomic sodium in the ground state in the photon-energy region close to the 2s threshold using the R-matrix method. We included five residual ${\mathrm{Na}}^{+}$ (2${\mathit{p}}^{6}$ $^{1}$S, 2${\mathit{p}}^{5}$3s $^{3}$${\mathit{P}}^{\mathit{o}}$, $^{1}$${\mathit{P}}^{\mathit{o}}$, 2s2${\mathit{p}}^{6}$3s $^{3}$S${,}^{1}$S) states in the R-matrix expansion. The initial Na ${(}^{2}$S) bound state, the final ${\mathrm{Na}}^{+}$ plus photoelectron ${(}^{2}$${\mathit{P}}^{\mathit{o}}$) state, and the residual ionic states are represented by fairly extensive configuration-interaction wave functions. The prominent features in the cross sections are two autoionization Rydberg series converging to ${\mathrm{Na}}^{+}$ (2s2${\mathit{p}}^{6}$3s $^{3}$S${,}^{1}$S) excited-state thresholds. The present results are compared with the available experiments.