Dynamics of three-body half collisions. II. Instantaneous three-body decomposition in the photodissociation of trifluoroacetyl iodidea)

Photofragment spectroscopy of trifluoroacetyl iodide (CF3COI) at 266 nm shows evidence of an instantaneous decomposition to I, CO, and CF3 fragments. The transition dipole moment for photon absorption lies in the C–C–O plane within 20° of the C–I bond axis, and decomposition of the photoexcited CF3COI molecule is rapid (∼10−13 sec). A two-step dissociation model developed to explain acetyl iodide photodissociation does not apply to trifluoroacetyl iodide, indicating fluorine substitution has a dramatic effect on photodissociation dynamics. Monte Carlo trajectory calculations using a very simple potential energy surface are surprisingly successful in predicting the observed dissociation behavior.