STRUCTURES IN THE ENERGY-DEPENDENCE OF THE RATE-CONSTANT FOR KETENE ISOMERIZATION

The isomerization of highly vibrationally excited and rotationally col d ketene has been investigated by monitoring the (CO)-C-12 and (CO)-C- 13 dissociation products following laser excitation of jet-cooled (CH2 )-C-12 (CO)-13, (CH2)-C-13 (CO)-C-12, and (CD2)-C-12 (CO)-C-13. The ra te constants for the reactions (CH2)-C-12 (CO)-C-13 half arrow right o ver half arrow left (CH2)-C-13 (CO)-C-12 and (CD2)-C-12 half arrow rig ht over half arrow left (CD2)-C-13 (CO)-C-12 are reported as a functio n of energy with a resolution of 1 cm-1. The rate constants exhibit pr onounced peaks as a function of energy near the reaction threshold. Th is structure is attributed to quasistable motion along the reaction co ordinate in the vicinity of the isomerization transition state.