Glassy Crystals VI. Nitrogen-14 Quadrupole Resonance in Glassy Crystalline Thiazole

Abstract

Crystalline thiazole has been studied by nitrogen-14 nuclear quadrupole resonance in the 77 - 206 K temperature interval that contains a glass transition at 174 K. The temperature dependences of the relaxation time T1 , of the frequencies and the amplitudes of the NQR signals have been determined for lines ν+ and ν-. No crystal-crystal phase transition has been observed, so that the glass transition at T'g can be observed on heating and on cooling. The T1 measurements have shown the existence of a large-amplitude motion which is different from that which is “frozen” at T'g: it corresponds to a secondary relaxation process which is still active in the glassy crystalline phase. Further studies will attempt to assign it to a definite molecular motion.