15min:

CHRISTOPHER J. ANNESLEY, ANDREW E. BERKE, F. FLEMING CRIM, The University of Wisconsin - Madison Department of Chemistry, 1101 University Avenue, Madison, WI 53705.

State-resolved reactions of CH₃D molecules with Cl atoms probe the consumption and disposal of vibrational and translational energy. Using state-resolved detection it is possible to determine the relative effects of these on the reaction and gain a better understanding of the reactivity differences between modes.

In one recent experiment, we explored the effect of exciting either the combination of the C-H symmetric stretch and the C-D stretch ( ₁ + ₂), the combination of the C-D stretch and the C-H antisymmetric stretch ( ₂ + ₄), or the combination of the C-D stretch and the first overtone of the CH₃ bend ( ₂ + 2 ₅). The reaction dynamics largely follow a spectator picture in which the surviving bond retains its initial vibrational excitation. In at least 80% of the reactive encounters of vibrationally excited CH₃D with Cl, cleavage of the C-H bond produces CH₂D radicals with an excited C-D stretch, and cleavage of the C-D bond produces CH₃ radicals with an excited C-H stretch. Deviations from the spectator picture seem to reflect mixing in the initially prepared eigenstates and, possibly, collisional coupling during the reaction.