Knowledge Bank

The low-lying electronic states of glyoxal in neat crystals and in both 3-methylpentane and 2-methyltetrahydrofuran glasses have been studied with optical spectroscopy at low temperature. The technique of PMDR was applied to facilitate assignment of the optical bands. Excitation spectra monitoring the phosphorescence and PMDR action spectra revealed an unusual enhancement of the $T1$ $\leftarrow$ $S0$ transition in the crystal and the ``milky” 3-methylpentane glass. A significant blue shift in the onset of absorption from the vapor at room temperature to crystals at $77\circ K$ was found. A description of these experiments and of other absorption, excitation, emission, and PMDR spectra in the crystal and the glasses will be presented.