Configuration interaction study of the O2–C2H4 exciplex: collision-induced probabilities of spin-forbidden radiative and non-radiative transitions
Abstract
The Collision complex between molecular oxygen and ethene has been studied by configuration interaction calculations, scanning the intermolecular distance in C2v collision symmetry. The calculations give a good explanation for the enhancement of the ethene T1â†� S0 and the oxygen A′3Δuâ†� X3Σ–g transition probabilities observed by Evans at high oxygen pressure. A number of other oxygen and cooperative transitions are explained and predicted, considering the studied system as a general model for unsaturated hydrocarbon–O2 interactions. The intermolecular potentials show negligible complex formation energies for the lower X3Σ–g, a 1Δg and b 1Σ+g states, but exciplex character for higher states. The ethene (ππ*) excited S1 state has a fairly deep minimum and a very strong transition moment to the T1 state, which also accounts for the non-radiative quenching of the hydrocarbon fluorescence by molecular oxygen.