PHOTOIONIZATION CROSS-SECTION WITH EXCITATIONS FOR NA

Many-body perturbation theory is applied to the calculation of photoio nization cross sections with excitations [2p, 3s] --> [4s, kl] and [3p , kl] of sodium. The double-electron excitations [2p,3s] --> [4s, nl] and [3p, nl] are included and lead to the resonance structure between 38.5 and 46.5 eV. The cross section for the transition (2p --> kd + ks ) is obtained taking into account the random-phase approximation (RPA) and an important part of the Breckner-orbital (BO) and structure-radi ation (SR) corrections. A comparison of the contributions from RPA, BO and SR for the transition (2p --> kl) is presented. The contributions of substantial correlations shake-off, virtual-Auger, knock-out and g round-state correlation (GSC) have been calculated and discussed for t he transitions [2p, 3s] --> [4s, kd] and [3p, kp], respectively. The r atios of the contributions from the cross section of photoionization w ith excitations to the cross section of the transition (2p --> kl) are in good agreement with experiment.