On the electronic energy disposal of calcium excited atom reactions with halogen-containing compounds: Electronic branching ratio and spin–orbit state populations Original Research Article

This paper reports on the electronic energy disposal of the Ca(1D2)+RX → CaX∗+R reaction system in which R=CH3, H and X=Cl, Br and I. The chemiluminescence yield was collected from either beam–gas or beam–beam reactions resolving the A and B electronically excited CaX states as well as the 2Π3/2, 1/2 spin–orbit states. The experimentally observed branching ratio, i.e. Γ(A/B) deviates significantly from the statistical value of 2 and hardly changes with collision energy. This deviation has been attributed to an increased role of Σ→Π transitions, i.e. the lack of orbital following as the impact parameter increases. In relation to the spin–orbit state population the overall behaviour is a nearly equally state population which, in principle, seems to be due to strong state mixing in these excited alkaline-earth halide reaction products. These findings are discussed in light of dynamical models currently used to interpret the reaction dynamics of excited species.