Phonon Effects in the uv Spectrum of Crystalline Hexamethylbenzene

Abstract
The intensity and linewidth of the 0–0 transition and some vibronic bands of crystalline hexamethylbenzene have been measured in the temperature range 4.2° to 70°K. It is found that the two components of the 0–0 transition polarized along the a′ and c′ axes, respectively, have different temperature dependence. The effect of phonons on the oscillator strength of very weak transitions is discussed.