Electric Quadrupole Relaxation of N14 in Ethylenediamine

A pulsed nuclear quadrupole resonance (NQR) spectrometer was constructed and with it the temperature dependences of relaxation of N 14 nucleus in ethylenediamine have been studied between 63 K and 274 K. As the temperature rises, two measured relaxation times, T 1s amd T 1 l which characterize the nuclear relaxation of the nitrogen NQR lines, approach gradually each other above 200 K. The obtained results show that the dominant relaxation mechanism below 140 K is attributed to the thermal torsional motion and that above 150 K is a molecular motion activated over the potential barrier of about 6 kcal/mol. A type of twisting motion of amino groups between two equivalent staggered cis positions is suggestive for the molecular motion.