Relative partial photoionization cross-sections and photoelectron branching ratios of ethylene

Abstract Relative partial photoionization cross-sections and photoelectron branching ratios of the valence bands (~10–25 eV binding energy) of ethylene are reported over the photon energy ranges 18–100 eV and 21–100 eV, respectively. The four lowest ionization energy bands (1 b −1 1u , 1 b −1 1g , 3 a −1 g , and 1 b −1 2u ) show monotonic cross-section decreases with photon energy from 33 eV, the 1 b −1 1u CC π band showing the least rapid decline. In contrast, the 2 b −1 3u and 2 a −1 g bands show almost constant cross-sections up to ~50 eV photon energy, followed by similar, although slower, monotonic decreases. This is attributed to the substantial carbon 2 s character of the 2 b 3u and 2 a g orbitais. The cross-section behaviour of all bands is interpreted with the aid of SCF-LCAO-MO calculations on the neutral molecule using the Gaussian-80 series of programs.