Electron Spin Resonance Spectrum of FCO

Abstract

The electron spin resonance spectrum of the fluoroformyl radical (FCO) has been observed at 4.2°K in solid carbon monoxide. The radical was prepared by reaction between the CO matrix and fluorine atoms produced by in situ photolytic dissociation of fluorine oxide (OF₂). The fluorine hyperfine splitting of FCO is very large and approximately axially symmetric: A₁/h=1437.5, A₂/h=708.2, and A₃/h=662.0 Mc/sec. The large hyperfine splitting results from spin polarization of an exceptionally weak CF bond, and is consistent with the theory for the proton hyperfine interaction in HCO. This implies that FCO, like HCO, is a sharply bent molecule in which the unpaired electron occupies an in‐plane or σ orbital, a conclusion which is in agreement with theoretical predictions.