Cl-35 NQR in glassy crystal of 2-chlorothiophene

Stable crystalline 2-chlorothiophene has two glass transitions at 164 and 1 86 K. Cl-35 NQR measurements were carried out between 77 and 200 K. Two NQR signals with full widths of about 100 kHz at half maximum were observed in this temperature range. The spin-lattice relaxation times T-1 were measure d at the two peak frequencies. The activation energy Delta epsilon(a), obta ined from the results of the T-1 measurements showed a fairly good agreemen t with those estimated from calorimetric measurements.