Molecular photoionization cross sections by the Lobatto technique. II. core level photionization

The logarithmic derivative Kohn-Lobatto (LDKL) method for determining molecular electronic continuum wave functions is applied to the calculation of core level photoionization cross sections. The description of the photoionization process is based on a local effective potential obtained from density functional theory. However, the LDKL method avoids a shape approximation to the potential like the muffin-tin form underlying the continuum multiple scattering (CMS) method. Different from the procedure for the investigation of valence photoionization the influence of the attractive hole has to be taken into account explicitly. Slater's transition state potential in the local density approximation (LDA) leads to very satisfactory predictions of photoionization cross sections and asymmetry parameters. This is demonstrated for the well known cases of N₂ and CO. Applications to the inner shell photoionization of SF₆ illustrate that the LDKL method in the present LDA implementation affords an efficient and accurate treatment of larger molecules for which it offers an alternative superior to the widely used CMSXα method.