Angle-resolved photoelectron spectroscopy of CO2 with synchrotron radiation

Abstract

The angular asymmetry parameter β has been determined for the first four bands in the photoelectron spectrum of CO2 as a function of photon energy: X 2Πg(15–50 eV), A 2Πu(19–28 eV), B 2Σu+(19–28 eV), and C 2Σg+(21–67 eV). Use is made of a monochromatized beam of photons from the Wisconsin Synchrotron Radiation Center. The experimental results are compared with theoretical calculations employing the multiple scattering method and the overall agreement is good. In addition, the theoretical predictions for the effect on β of shape resonances have been verified except that the experimental widths are broader. This broadening has been partially accounted for in recent calculations of Swanson et al. by including the effects of vibrational motion. Finally, sharp changes in β as a function of vibrational level have been noted for the second and fourth electronic bands. Such behavior has been found for a variety of photon energies, and the results are examined against prevailing theory.