Triplet dynamics of benzaldehyde as studied by electron impact excitation

Electron-impact-induced luminescence was measured for benzaldehyde at low vapor pressure. Phosphorescence bands from the zero-point level of T 1 were observed at 397.427, and 460 nm. The pressure dependence of the phosphorescence decay rate was found to be essentially the same as that obtained by optical excitation. In addition to these bands, closely spaced, weak emission bands were observed. These emissions were found to have much shorter lifetimes than the phosphorescence from the zero-point level and to be sensitive to collisional quenching. We assign the latter bands to the phosphorescence from vibrationally excited T 1 molecules.