POLARIZATION OF THE PHOSPHORESCENCE OF PHENANTHRENE

Abstract

“Measurements of the polarization of the phosphorescence of phenanthrene are being made in an attempt to assign the lowest triplet electronic state in this molecule. Phenanthrene, dissolved in EPA glass at $77^{\circ} K$ is irradiated with polarized light and the polarization of the emitted phosphorescent light is measured. McClure has determined that the lowest singlet-singlet transition lies in the plane of the molecule and is short axis polarized. It has been shown that irradiation with light absorbed in this transition gives negatively polarized phosphorescence. This requires that the phosphorescence transition be polarized either perpendicular to the ring plane or in the ring plane along the long axis of the molecule. To decide between these possibilities it is necessary to use exciting light which is absorbed in a higher singlet-singlet transition which is polarized perpendicular to the lowest singlet-singlet transition. The latter experiment is in progress at the time of writing.”