Calculated photoionization cross sections and relative experimental photoionization intensities for a selection of small molecules

• Published in: The Journal of chemical physics 1974-07, Vol.61 (2), p.516-528
• Main Authors: Rabalais, J. Wayne, Debies, Thomas P., Berkosky, Jeffrey L., Huang, Jan-Tsyu J., Ellison, Frank O.
• Format: Article
• Language: English
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/1.1681926

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.