The lowest singlet state of dibenzofuran

The vapor absorption of dibenzofuran has been reexamined, and the spectrum and lifetime of the vapor fluorescence have been measured. Also measured were the polarized absorption in durene host and the depolarized absorption, fluorescence, and phosphorescence in cyclododecane host at 4 K. The fluoresecent state is that corresponding to the 3000 Å absorption in all media, and no evidence was found for a weak transition at 3175 Å as reported by Pinkham and Wait. The mixed crystal spectra are heavily perturbed, but from the polarizations observed in durene the 3000 Å transition is assigned as ${}^1\text{B}{}_2\text{←}{}^1\text{A}{}_1$ (long axis polarized).