Excitation of lower autoionization S-1 states of the helium-like ions in x-ray scattering

The process of inelastic scattering of high-frequency photons leading to ex citation of singlet autoionization states (AIS) with total angular momentum L = 0 located below the first excited level of the respective one-electron ion are considered. For the amplitude of the process analytical expressions are derived, which include one-dimensional integrals, the latter being evaluated numerically. The scattered photon angular distributions and the absolute cross section o f the considered process are obtained. The transitions into two lower S-1 A IS are investigated. The approximation is employed, in which the electrons are described by Coulomb functions, and their interaction is taken into acc ount in the first order of the perturbation theory. The correct AIS functio ns of the zero approximation are used which are obtained as solutions of th e secular equation.