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 (2) Sigma(+) (v' = 0), B (2) Sigma(-) (v' = 0, 1) and A(2) Delta (v' = 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(1)B(1)) 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(1)B(1)) 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.