Polarization of the Phosphorescence of Naphthalene and Phenanthrene

Abstract

Polarization of the phosphorescence of naphthalene and phenanthrene has been observed. The substances were dissolved in EPA glass at 77°K and irradiated with plane polarized exciting light sufficiently monochromatic to be absorbed by only a single electronic transition. The phosphorescence transition is perpendicular to the plane of the ring for phenanthrene and lies in the plane of the ring along the short axis for naphthalene. Comparison of observed polarizations with those predicted for various assignments of the lowest triplet shows that no assignment can be made in the case of phenanthrene. An assignment may be possible in the case of naphthalene though it is subject to uncertainty because of the contribution to the emission intensity which may be due to vibrationally induced transitions.