Dispersed fluorescence spectroscopy of S0 formyl fluoride vibrational states

Dispersed fluorescence (DF) spectroscopy was used to record a 22 500 cm(-1) spectrum of the vibrational energy levels of formyl fluoride (HFCO) and thereby determine harmonic frequencies and anharmonic constants for the S-0 potential energy surface. Sample molecules were cooled in a supersonic expansion and excited to low J, K-a = 0 rotational states in the 6(2) vibrational level of S-1 HFCO, and the resulting fluorescence was dispersed from 255 to 600 nm, Long progressions in the CO stretch (v(2) = 0-6) and out-of-plane bend (v(6) = 0-23) and shorter progressions in the CF stretch (v(4) = 0-2) and FCO bend (v(5) = 0-2) are observed. Analysis of the spectrum results in 240 assignments, including 196 new assignments and 56 assignments above the approximate 17 000 cm(-1) dissociation threshold. The data are fit to an anharmonic oscillator model with a standard deviation of 3.3 cm(-1).