Knowledge Bank

The 333 nm ($\Pi$,$\Pi \ast$) transition of pyrimidazole has been observed in absorption spectra of the vapor and in doped naphthalene and naphthalene-$d8$ crystals. The vapor phase origin occurs at $30035cm-1$ with three site origins observed in the mixed crystal spectra with contrasting phonon structures. The prominent vibrational frequencies observed in vapor spectra are $270,398,604,749.760,850,902,1006,1108,1176,1188,1268,1335,1367$, and $1562cm-1$ Crystal spectra show with very small matrix shifts the $398,604,760,902$, and $1108cm-1$ vibrational modes. Work is continuing to refine the polarizations of the observed features and to correlate excited state vibrational frequencies with ground state frequencies obtained from infrared and Raman studies.