ROTATIONAL ANALYSIS OF THE B(2)A''-X(2)A'' ORIGIN BAND OF THE CH2CFO RADICAL

The laser fluorescence excitation spectrum of the origin band of an el ectronic transition in the CH2CFO radical was recorded with partial ro tational resolution using a supersonic, rotationally cold beam. The ra dical was prepared in a pulsed free jet by 193 nm photolysis of acetyl fluoride diluted in helium or argon. The rotational structure of the band is consistent with an in-plane electronic transition of this near oblate rotor. In analogy with the vinery radical, this transition is designated as (B) over tilde(2)A''-(X) over tilde(2)A''. Spectroscopic constants were derived from a fit to the assigned rotational transiti ons. The lower state rotational constants agree with those calculated from an ab initio CH2CFO equilibrium structure [M. Furubayashi, I. Bri dier, S. Inomata, N. Washida, and K. Yamashita, J. Chem. Phys. 106, 63 02 (1997)]. The present study thus provides confirmation of the assign ment of the molecular carrier as CH2CFO and eliminates the alternative assignment to FCO [B. A. Williams and J. W. Fleming, J. Chem. Phys. 1 06, 4376 (1997)]. (C) 1997 American Institute of Physics. [S0021-9606( 97)01547-X].