Knowledge Bank

The polarized excitation spectrum of the $C\ast$ molecule benzaldehyde in rigid hydrocarbon media was studied with reference to the polarized 0-0 band of the phosphorescence. Previous $work1$ indicated the apparent presence of at least two vibrational progressions of opposite polarization. The present study at higher resolution, using a Baird-Atomic SF-1 Fluorispec shows that the most intense sequence is a totally symmetric progression polarized perpendicular to the molecular plane, with the weaker progression polarized predominantly along the carbonyl-ring axis. Comparison with $benzaldehyde-d1$ and with the vapor $spectrum2$ allows a vibrational analysis and makes possible an assessment of the allowed vs vibronic sources of intensity.