Fluorescence of CF2(1B1, 040,K' = 9) excited by the 253.7 nm Hg resonance line

Resonance fluorescence spectra of CF 2 ( 1 B 1 , 040, K' = 9) excited at 253 7 nm have been observed in the photolysis of C 2 F 4 using a low-pressure mercury lamp. At low C 2 F 4 pressures, the spectra with a series of doublet hands from 254 to 400 nm were consistent with the transitions from 1 B 1 , 040, K' =9 to 1 A 1 , 0 v'' 2 0, K'' = 8, 10, and also to 1 A 1 , 1 v'' 2 0, K'' = 8, 10 The appearance of doublet bands (Δ K = ±1) provides clear evidence that the transition is of the perpendicular type.