THE NEAR-ULTRAVIOLET DISSOCIATION DYNAMICS OF AZOMETHANE - CORRELATEDV-T ENERGY DISPOSAL AND PRODUCT APPEARANCE TIMES

We have measured the translational energy release for methyl radical p hotofragments with zero and one quantum of umbrella vibration, which w ere produced by the ultraviolet dissociation of azomethane, Translatio nal energy distributions exhibit bimodal structure and are similar for both methyl radical vibrational states and for two dissociation wavel engths (355 and 330 nm). Compared to earlier non-state-selective measu rements, these distributions exhibit a stronger preference for high ki netic energies. We have also observed that the appearance times for bo th methyl radical vibrational states are fast compared to the experime ntal time resolution, thus resolving an outstanding mechanistic disagr eement. These observations are consistent with a previously proposed m echanism in which a concerted three-body dissociation follows randomiz ation of parent internal energy, (C) 1998 American Institute of Physic s. [S0021-9606(98)01941-2].