The general equations for calculating photoionization cross sections of polyatomic molecules in the plane-wave and orthogonalized plane-wave approximations have been programmed for the electronic computer. Applications are described for the molecules H2, CH4, N2, CO, H2O, H2S, and H2CCH2 for incident photon energies from threshold to 1500 eV. Relative experimental photoionization band intensities for the above molecules are measured using NeI, HeI, and HeII resonance radiation. A simplified analysis of the intensities derived from electrostatic deflection analyzers is presented. The 2P3/2:2P1/2 intensity ratios of the rare gases are determined with the three modes of excitation mentioned above. An analysis of the resolution capabilities of an electrostatic deflection spectrometer as a function of electron kinetic energy is presented. Relative experimental photoionization band intensities for the above molecules obtained by ionization with the three uv sources and MgKa and A1Ka x-ray sources are compared with computed differential cross sections. Variations in computed cross sections as a function of the kinetic energy of the photoelectrons are discussed and possible interpretations are proposed.
The general equations for calculating angular distributions of photoelectrons within the orthogonalized plane-wave approximation have been programmed for the electronic computer. Applications are described for the molecules CH4, H2O, and N2 with incident photon energies from threshold to 1254 eV. Computed values of the asymmetry parameter β are compared to experimentally determined β values using HeI excitation. Large variations in β as a function of photon energy are obtained; possible interpretations are proposed.
A semiempirical model has been developed for estimating spin-orbit interactions in molecular ion states derived by ionization of closed-shell neutral molecule states. A perturbation approach is used with an effective spin-orbit interaction operator H so and approximate Mulliken-Wolfsberg-Helmholz molecular orbital (MO) wavefunctions. Effective spin-orbit parameters tv were obtained by interpolation with respect to atomic charges derived from the MO calculations. The He I photoelectron spectra of the PXlX = CI, Br, I) and PYX 3 (X = CI, Br; Y = 0, S) series have been measured. Splittings observed in some of the ionization bands of this series have been successfully interpretated as spin-orbit splittings using the newly developed model.
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