Photodissociation of the vinyl radical (C2H3) via the first excited state: The C2H2(X1Σg+)+H channel

Photodissociation of C2H3 via its first excited Ã2A″ state is studied at 327.4 and 366.2 nm using high-n Rydberg-atom time-of-flight technique. C2H2(X̃1Σg+)+H product channel is identified. Product translational energy distributions reveal two highly-inverted vibrational progressions of C2H2(X̃1Σg+) (most likely C≡C stretch and its combination band with C–H bend). Anisotropic H-atom angular distributions indicate a short Ã2A″ state lifetime with respect to dissociation. D0(C2H2–H)=33.0±0.5 kcal/mol is obtained.