Excitation Probabilities of Singlet and Triplet States

Abstract

IT has long been known from experimental evidence¹ that triplet states in the spectra of two electron systems differ from the corresponding singlet states in their behaviour to electron impact. The probability of excitation of a triplet level has a sharp maximum for electron energies just above the excitation potential, whereas in the case of singlets the maximum probability is not sharp, and occurs at energies considerably beyond the resonance potential; also, for high velocities the triplet excitation is negligible compared with the singlet excitation. The difference must lie in the fact that the triplets can only be excited from the ground state by electron exchange, and Oppenheimer² has shown in general how this may be approximately calculated.