Optically Detected Low Temperature Phase in Pyrene Crystals

Abstract

Absorption and luminescence spectra in pyrene have been investigated. Absorption spectra below the phase transition point at 120 K exhibit structures which are not observed in the room temperature spectra. Below the phase transition temperature another dimeric phase (α′) which differs from that in the room temperature phase (α) is suggested to appear. This suggestion is consistent with information reported from the electron diffraction patterns. The relationship between the specimen cooling method and the occurrence of the phase transition is briefly discussed.