Dynamics of three-body half collisions. I. Secondary product decomposition in the photodissociation of acetyl iodide

Abstract

Photofragment spectroscopy of acetyl iodide (CH3COI) at 266 nm shows evidence of a two-step dissociation into three products. Initial photodissociation yields an iodine atom and a highly internally excited acetyl radical containing on average 80% of the energy available in the dissociation process. The transition dipole moment of the initial absorption lies in the C–C–O plane near the C–I bond axis, and breakup of the photoexcited acetyl iodide is rapid, on the order of 10−13 sec. The acetyl fragment is found to live for several rotational periods, ∼10−11 sec. Its subsequent decomposition to CO and CH3 can be modeled by statistical theories of unimolecular decay. It is found that an average 30% of the energy residing in the acetyl radical ultimately appears as relative translational energy of the CO and CH3 fragments.