RESONANCE STRUCTURE IN THE 2P PHOTOIONIZATION OF ATOMIC SODIUM CLOSE TO THE 2S THRESHOLD

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 Na+ (2 p(61)S, 2p(5)3s P-3(0), P-1(0), 2s2p(6)3s(3)S, S-1) states in the R-ma trix expansion. The initial Na (S-2) bound state, the final Na+ plus p hotoelectron (P-2(0)) state, and the residual ionic states are represe nted by fairly extensive configuration-interaction wave functions. The prominent features in the cross sections are two autoionization Rydbe rg series converging to Na+ (2s2p(6)3s(3)S,S-1) excited-state threshol ds. The present results are compared with the available experiments.