title: (14)N 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 T1 is interpreted as due to hindered rotation of the NO2 group about the C-NO2 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.
authors.affiliation: Department of Informatics, King's College London, Strand, London WC2R 2LS, UK.
authors.forename: John A S
authors.initials: JA
authors.lastname: Smith
authors.affiliation: Department of Informatics, King's College London, Strand, London WC2R 2LS, UK. Electronic address: michael.d.rowe@kcl.ac.uk.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Rowe
authors.affiliation: Department of Informatics, King's College London, Strand, London WC2R 2LS, UK. Electronic address: k.althoefer@kcl.ac.uk.
authors.forename: Kaspar
authors.initials: K
authors.lastname: Althoefer
authors.affiliation: Angel House, Marsh Lane, Saundby, Retford DN22 9ES, UK. Electronic address: nqr2004@yahoo.co.uk.
authors.forename: Neil F
authors.initials: NF
authors.lastname: Peirson
authors.affiliation: Department of Informatics, King's College London, Strand, London WC2R 2LS, UK. Electronic address: jamie.barras@kcl.ac.uk.
authors.forename: Jamie
authors.initials: J
authors.lastname: Barras
keywords: (14)N NQR; NQR parameters; NQR relaxation times; Pulsed spin-locking (PSL) sequence; TNT detection; Temperature variation