Polarized fluorescence spectra of retinol ad diphenyl octatetraene

The polarization of fluorescence excitation and emission bands of all-trans retinol in 77°K has been measured at relatively high resolution. The main excitation band as well as the fluorescence band showed a degree of polarization approaching that the theoretical maximum of 0.5 for a linear oscillator under photoselective conditions. These results are consistent with the assignment that the main absorption and fluorescence bands originate from the long-axis polarized ⁱB ← ^IA transition, as expected from free electron theory. Diphenyl octatetraene was also studied, yielding results similar to the retinol system.