Microwave Spectrum and Barrier to Internal Rotation in Trifluoronitromethane

Abstract
The microwave spectrum for CF3NO2 has been observed for the J = 1→J = 2 through the J = 4→J = 5 transitions. Some 35 lines in these transitions are assigned, and the Stark effects for three of these were studied quantitatively and interpreted. A discrepancy in the Stark effect of a 4→5 transition can be accounted for by properly adjusting the sixfold barrier to internal rotation. The parameters used to obtain the best fit for the spectrum are the following: B + C = 4917.4±0.4 Mc/sec, BC = 453.9±5 Mc/sec, A (NO2) = 13205±150 Mc/sec, A (CF3) = 5700 Mc/sec (assumed), V6 = 780 000 Mc/sec = 74.4±5 cal/mole. The dipole moment obtained from the Stark‐effect measurements is 1.44±0.03 D.
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