Fluorescence studies on photo-induced structure changes in purified biphenyl crystals

Fluorescence spectra of pure biphenyl crystals were measured over a wide te mperature range. In contrast to the sharp peaks near 530 nm observed in cry stals grown from methyl alcohol solution, a new broad band around 500 nm wa s found in zone-refined crystals at 5.0 K when the intense exciting laser w as employed. From the temperature dependent behavior and the fluorescence d ecay characters, it is suggested that the new excimer-like band is related to photo-induced structural deformation in biphenyl crystals.