Abstract: A novel experimental technique to measure the energy- dependent unimolecular dissociation rate k(E) of radical species is presented. Internally excited CH$-3$/CO radicals were formed by ultraviolet photodissociation of CH$-3$/COCl, and the subsequent decay of these radicals was detected by subpicosecond time-clocked photofragment imaging. The CH$- 3$/CO radicals with different internal energies were dispersed in space by their recoil velocities, and their decay rates were measured for each internal energy. !16
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