Abstract: Vinyl radical was generated by photolysing methyl vinyl ketone at 193 nm, then was photodissociated by another tunable laser in the 21180~21320 cm1 range. The dissociated H atom fragments were ionized and detected by resonance-enhanced multiphoton ionization (REMPI) processes. The ro-vibrational action spectra of the A2A″(µ′5,6,8=1)←X2A′(µ″=0) of vinyl radical were recorded by monitoring the H+ ion intensity with dissociation laser wavelength. The corresponding analyses were obtained with the aid of quantum chemical calculations and spectroscopic simulations, vibrational bands and main rotational transitions were definitely assigned. Additionally, the predissociative lifetime was derived from the simulated linewidth, and its dependence on the vibrational mode and rotational quantum number was discussed. The in-plane dissociation mechanism of the state predicted by theoretical studies was confirmed.

Key words: Vinyl radical, Resonance-enhanced multiphoton ionization (REMPI), Pre-dissociation