Detection of the perpendicular A state transitions of CH3I by imaging of photofragment angle-velocity distributions

Photofragment angle-velocity distributions are measured in a molecular beam using a new two-dimensional imaging technique. We report on the detection of weak perpendicular transitions for CH3I Ã state photodissociation at 266 and 304 nm. The ratio of cross sections and the 3Q0−1Q crossing probability are σ⊥/σ∥=0.00−0.10 and p=0.22−0.27 at 266 nm and σ⊥/σ∥=0.20−0.30 and p=0.43−0.48 at 304 nm.