The microwave spectrum of the trifluoromethyl radical

Abstract

The microwave spectrum of the trifluoromethyl radical in the ground 2A1 state has been observed by using a source frequency modulation spectrometer. The CF3 radical was generated directly in the absorption cell by a glow discharge in trifluoroacetic acid anhydride (CF3CO)2O. The observed transitions included N = 4←3, 5←4, and 6←5, all of which are resolved into K as well as fine and hyperfine structure components. A magnetic hyperfine Hamiltonian was derived for three identical nuclei with a spin of 1/2 (the fluorine nuclei) in a doublet symmetric-top molecule, in order to analyze the observed spectrum. Most of the hyperfine structure could be explained by considering the total nuclear spin operator I0 = ΣiIi, except for the K = 1 transitions; some of them were clearly resolved into doublets and the observed splittings allowed us to determine the additional dipole-dipole hyperfine interaction constant |T∞-Tbb|. The rotational constant B 0 was determined to be 10 900.9118(52) MHz, with 2.5 times the standard error given in parentheses, and the unpaired π-electron spin density on each fluorine atom was estimated to be 12.3% from the observed hyperfine coupling constants. © 1982 American Institute of Physics.