The 3000 Å Absorption Spectrum of Phenanthrene in Mixed Crystals

Abstract

The polarized second singlet-singlet absorption spectrum of phenanthrene at 3000 Å has been observed in mixed crystals of durene and hexamethlbenzene. In durene at 4 °K, bandwidths of 10cm⁻¹ are observed and lattice vilbrations identified. Electron spin resonance measurements of the phenanthrene triplet in durene have shown that the orientation of the phenanthrene is changed from that of the durene. Nevertheless the observed polarization ratios are close to those calculated for a long-axis polarized mixed crystal transition. All the results are in agreement with the assignment of ¹B₂ for the second singlet state.