The spectra of the X̃2A′-Ã2A″ electronic transition of jet-cooled vinyl radical, C2H3, and its partially deuterated isotopomer, CD2CH, have been obtained via action spectroscopy. The appearance of the H or D fragment was monitored via 1+1′ resonance enhanced multiphoton ionization through the Lyman-α transition. The vibrational structure of the Ã2A″ state was fully resolved and analyzed. The experimental vibrational frequencies agree well with ab initio calculations. The simulation of the rotational structure of several bands reinforces vibrational assignments.

H or D atom velocities are reported for dissociation from several vibrational levels in the lowest 2500 cm−1 of the Ã 2A″ state of two vinyl radical isotopomers, C2H3 and CD2CH. Energies are inferred for the acetylene product and compared with both theoretical and experimental work. An upper bound is given for the rate of H-atom scrambling between the α and β carbon atoms.