14N NQR, relaxation and molecular dynamics of the explosive TNT

Abstract

Multiple pulse sequences are widely used for signal enhancement in NQR detection applications. Since the various 14 N NQR relaxation times, signal decay times and frequency of each NQR line have a major influence on detection sequence performance, it is important to characterise these parameters and their temperature variation, as fully as possible. In this paper we discuss such measurements for a number of the ν + and ν − NQR lines of monoclinic and orthorhombic TNT and relate the temperature variation results to molecular dynamics. The temperature variation of the 14 N spin-lattice relaxation times T 1 is interpreted as due to hindered rotation of the NO 2 group about the C-NO 2 bond with an activation energy of 89 kJ mol -1 for the ortho and para groups of monoclinic TNT and 70 kJ mol -1 for the para group of orthorhombic TNT.

Solid‐state nuclear magnetic resonance and nuclear quadrupole resonance as complementary tools to study quadrupolar nuclei in solids

“…NQR is commonly performed on nitrogen‐14 ( I = 1) and has been shown to be a potentially effective technique for routine analysis in the fields of explosives and pharmaceuticals . As a result of its moderate quadrupole moment ( Q ( 14 N) = 20.44(3) mb), and lack of a central transition, 14 N SSNMR can be experimentally challenging to perform due to the first‐order quadrupolar broadening.…”