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 CC 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.