Abstract: The vinyl radical was generated by photolysing methyl vinyl ketone with 193 nm laser, then was excited and photodissociated by another laser in the 20020～20070 cm_-1 range. The dissociated H atom fragments were ionized and detected by (1+1′) resonance-enhanced multiphoton ionization (REMPI) process. The rotationally resolved action spectra of theA²A''(v'=0)←X²A'(v''=0)band of the vinyl radical were recorded by monitoring the H⁺ ion intensity with dissociation laser wavelength. The corresponding assignments were obtained with the aid of ab initio calculations and spectroscopic simulations, and 40 rotational lines were definitely assigned. Additionally, the predissociative lifetime of the •C₂H₃ A²A''(v'= 0 ) state was 3.3 ps and independent of the rotational levels, which was derived from the linewidth.

Key words: Vinyl radical, Resonance-enhanced multiphoton ionization, Rotational spectroscopy, Predissociation