Angular distribution of photoelectrons from free molecules of N2 and CO as a function of photon energy

Abstract

The asymmetry parameter beta for the isoelectronic molecules N₂ and CO has been measured using the 5 GeV electron synchrotron NINA at the Daresbury Laboratory to provide elliptically polarised radiation over the energy range 20 to 45 eV. beta values for each of the ionic states X² Sigma , A² Pi and B² Sigma are presented which are in good agreement with existing measurements at 21.2 eV. The data, however, show significant variations in beta with photon energy. Comparison is made with existing calculations and qualitative explanations are offered for several discrepancies between theory and experiment. The data are, however, considerably at variance with theory for the CO⁺B² Sigma ⁺ state and less so for the corresponding N₂⁺B² Sigma _u⁺ state.