The nature of optical spectra of p-terphenyl

The absorption, fluorescence and fluorescence excitation spectra of p-terphenyl (TP) crystals have been investigated. The absorption spectrum of a thin (1 μm, 5 K) crystal shows several electron transitions with a strongly and weakly developed vibrational structure. It is found that even the purest TP crystals contain a large number of uncontrolled impurities absorbing in the region 331 – 390 nm, and the crystal fluorescence spectrum reported in the literature is due to the defect-impurity emission.