Photodissociation of ketene with a narrow-band tunable laser around 212.5 nm

The photodissociation of ketene with a narrow-band tunable laser has been studied at 218.0, 212.5 and 207.0 nm. A CH photofragment is formed in the C 2Σ+ (ν′ = 0), B 2Σ− (ν′ = 0, 1) and A 2Δ (ν′ = 0, 1) states through a process involving the absorption of two laser photons. The visible emission observed above 580 nm is attributed to the CH2(b 1B1) photofragment formed in a single-photon process. The experimental results strongly suggest that electronically excited CH could be formed in a sequential mechanism involving the absorption of a second photon by the CH2(b 1B1) intermediate. Nevertheless, the simultaneous existence of several mechanisms must be considered to explain the formation of the CH fragment in the various observed electronic states.