Determination of the barrier height to CH₃CO dissociation

The photodissociation of acetyl chloride at 248 nm has been investigated by the technique of photofragment translational spectroscopy. A comparison of the transitional energy distributions required to fit the chlorine atom and the acetyl radical indicates that a significant fraction (≈ 35%) of the CH₃CO fragments undergo secondary decomposition to CH₃ and CO. From analysis of the center-of-mass translational energy distributions a value of 17 ± 1 kcal/mol for the barrier height to acetyl radical dissociation has been determined.