Electronic Spectra of Phenanthrene in Mixed Crystals

Abstract

The analyses of the 3500‐Å polarized absorption, fluorescence (¹A₁⇄¹A₁) and phosphorescence (∼4500 Å, ³B₂→¹A₁) spectra of phenanthrene —h₁₀ and d₁₀ (guests) substitutionally dissolved in a biphenyl‐(host)‐crystal lattice are reported. Considerable attention is given to the role of intramolecular vibronic coupling in the electronic transitions of phenanthrene and a number of vibronic coupling pathways have been elucidated. Several manifestations of guest—host interactions in the phenanthrene spectra have been observed and in particular, evidence is given to show that certain vibronic states of the first excited‐singlet‐state manifold crystal field mix with the states of the host (biphenyl, fluorene) more effectively than others. The multiplet structure of the vibronic bands in the electronic spectra of phenanthrene in biphenyl previously reported is shown in detail.