ON THE ELECTRONIC-ENERGY DISPOSAL OF CALCIUM EXCITED ATOM REACTIONS WITH HALOGEN-CONTAINING COMPOUNDS - ELECTRONIC BRANCHING RATIO AND SPIN-ORBIT STATE POPULATIONS

This paper reports on the electronic energy disposal of the Ca(D-1(2)) + 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 Ca X states as well as the (2)Pi(3/2,1/2) spin-orbit states. The experime ntally observed branching ratio, i.e. Gamma(A/B) deviates significantl y from the statistical value of 2 and hardly changes with collision en ergy. This deviation has been attributed to an increased role of Sigma --> Pi transitions, i.e. the lack of orbital following as the impact parameter increases. In relation to the spin-orbit state population th e overall behaviour is a nearly equally state population which, in pri nciple, seems to be due to strong state mixing in these excited alkali ne-earth halide reaction products. These findings are discussed in lig ht of dynamical models currently used to interpret the reaction dynami cs of excited species. (C) 1998 Elsevier Science B.V. All rights reser ved.