Temperature and Pressure Dependence of the Nuclear Quadrupole Resonance of 14N in (CH2)6N4

Abstract

The pure nuclear quadrupole resonance frequency of ¹⁴N in hexamethylenetetramine has been studied as a function of pressure and temperature. At constant (atmospheric) pressure the temperature dependence was studied from 4.2° to 340°K. The isothermal pressure dependence was measured at three temperatures, 77°, 196°, and 299°K. These data were analyzed by two methods. In one case, following the method of Brown, the torsional frequency of vibration of the molecules is assumed to decrease as the temperature increases, and this temperature dependence is determined by fitting the quadrupole frequency temperature dependence at atmospheric pressure with Bayer theory. In the second method the volume dependence of the NQR frequency is determined following the method of Kushida, Benedek, and Bloembergen; the parameters involved in this case are found to be intrinsically temperature dependent.