The correlation between 1(2P3/2)/I(2P1/2) branching and CH3 rotation in photolysis of single quantum state-selected CH3I (JK=11)

The dependence of the I(P-2(3/2))/I(P-2(1/2)) branching ratio on the end-over-end rotational state of the methyl photo-fragment, CH3 (nu(2) = 2\N, K = 1), after photodissociation at 266 nm of single quantum state-selected CH3I (JK = 11) molecules is reported. Using velocity map imaging the spatial velocity distribution of the vibrationally excited CH3 (nu(2) = 2) photoftagment was detected. The I(P-2(3/2)) and I(P-2(1/2)) yields were extracted from the speed distribution of rotationally selected CH3 (nu(2) = 2\N, K = 1) photofragments. Quantitative analysis shows a strongly increasing I(P-2(3/2))/I(P-2(1/2)) branching ratio with increasing CH3 end-over-end rotational motion, in reasonable agreement with recent three-dimensional state-to-state ab initio calculations. (C) 2002 Elsevier Science B.V. All rights reserved.