INNER-SHELL PHOTOIONIZATION OF SODIUM : EXPERIMENT AND THEORY

Recent measurements of the photoionization of Na by ejection of a $3s,$ $2p,$ or $2s$ electron give branching ratios, \ensuremath{\beta} parameters, and absolute partial cross sections for a number of excitation processes, allowing one to perform the full partition of the total photoabsorption cross section into its components. In parallel, recent developments of the $R$-matrix code, together with extensive configuration and close-coupling expansions, make it possible to calculate the relevant quantities over the continuum energy range (40--140 eV) as well as in the resonant energy region corresponding to the excitation of a $2p$ or $2s$ inner-shell electron onto empty optical orbitals. A critical comparison is made of our experimental results with previous and present theoretical calculations. Valuable information is obtained for the ionization energies and relative cross sections. The main limitation in testing the validity of the various theoretical approximations is the lack of accuracy of the experimental photoabsorption cross section measured only to about 25%.