Cross section and asymmetry parameter calculations for the C 1s photoionization of CH₄, CF₄, and CCl₄

We have computed cross sections and asymmetry parameters for the C 1s photoionization of CX₄ (X=H, F, Cl) using the Schwinger variational method with Padé corrections. We present a comparative study that shows the influence of the identity of the X atom on the computed cross sections. Predicted cross sections are in good agreement with available photoionization and photoabsorption experimental data. We conclude that the presence of heavy outer atoms produces resonance structures in the photoionization cross sections and in the asymmetry parameters. We find a single nonvalence resonant state in the photoionization of CF₄ and multiple resonances in CCl₄ that have significant d-orbital character in the vicinity of the Cl atoms.