Electron nuclear double resonance of photoexcited phenanthrene-d10 molecules in their lowest triplet state in diphenyl single crystals

Electron deuteron double resonance spectra have been obtained for phenanthrene-d10 molecules in their triplet electronic state of lowest energy, when they are dilutely substituted in a diphenyl host crystal. Four discretely different orientations of phenanthrene-d10 molecules at the same set of translationally equivalent substitution sites of the diphenyl host, have been observed. Values of hyperfine interaction tensor components and of spin densities for these different phenanthrene-d10 molecules have been determined. The distortions of these various molecules from an ideal symmetry and the importance of these different distortions, as well as of the different orientations, for the interpretation of the intensities and polarizations of optical spectra, are discussed in light of the present measurements.