Ab initio calculation of the photoionization cross sections and photoelectron angular distribution parameters of CH4, NH3, H2O and CO

Photoionization cross sections sigma(n gamma) (omega) and photoelectron angular distribution parameters beta(n gamma) (omega) are systematically computed for the closed-shell molecules CH4, NH3, H2O and CO. Calculations are performed by the single center (SC) method based on the numerical integration of the coupled Hartree-Fock equations for a photoelectron in continuum. In the cases of the core n gamma(1s) and valence n gamma(2p) molecular orbitals, a good overall agreement between the present theory and experiment available in the literature is obtained. For the subvalence n gamma(2s) molecular orbitals, agreement between the theory and available experiment is satisfactory, which can be attributed to an impact of many-electron correlations neglected in the present calculations.