AbstractThe Raman spectral bandwidths of twoA1′ vibrations of 1,3,5‐trifluorobenzene (TFB) were measured in the neat liquid as a function of temperature and in the solvents CH2Cl2and CS2. The Raman and IR linewidths of twoE′ modes were also measured in solution. Derived values of the two rotational diffusion constants,D⊥andD∥, were compared with the predictions of several current theories. It was observed that the Hynes–Kapral‐Weinberg (HKW) theory is superior to both the microviscosity–free rotor and Hu–Zwanzig ‘slip’ models of reorientational diffusion. Calculated values ofD⊥andD∥for TFB in solution using the HKW model are in excellent agreement with the experimentally mea