Theoretical equations for photoionization cross sections of polyatomic molecules in plane-wave and orthogonalized plane-wave approximations

• Published in: The Journal of chemical physics 1974-07, Vol.61 (2), p.507-515
• Main Author: Ellison, Frank O.
• Format: Article
• Language: English
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/1.1681925

The general polyatomic molecule in a closed-shell electronic state with nuclei fixed according to the Born-Oppenheimer approximation is photoionized to form a final singlet state in which one electron is excited into the continuum. All bound orbitals are assumed identical in the initial and final states. The unbound orbital is approximated either by a plane-wave or by a plane-wave orthogonalized to all occupied bound orbitals. Formulations are given for cases in which bound orbitals are expressed as linear combinations of Slater-type orbitals, orthogonalized Slater-type orbitals, Cartesian Gaussian-type orbitals, or Gaussian-lobe functions. General equations are derived for the photoionization cross section of randomly oriented polyatomic molecules as a function of angle between the polarization vector of the photon beam and the propagation vector of photoejected electrons. Also derived is the photoionization cross section of the same sample as a function of angle between an unpolarized photon beam and the propagation vector of photoejected electrons.