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Proceedings Paper

Low temperature dielectric properties of ammonium nitrate in terahertz regime
Author(s): Abdur Rahman; David S. Moore; Abul K. Azad
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Paper Abstract

Terahertz (THz) spectroscopy is a nondestructive method that has the ability to identify many hazardous materials by investigating their low frequency vibrational modes (0.1-6.0 THz). Ammonium nitrate (AN), often used in improvised explosives, exhibits featureless reflection/transmission spectrum at THz frequencies at room temperature. However, the low frequency vibrational modes exhibit strong temperature dependence below room temperature (<240k) due to the polymorphic phase transitions. In this work, we study the effective dielectric properties of AN embedded in a polytetrafluoroethylene (PTFE) host medium using terahertz time domain spectroscopy in the temperature ranging from 5K to 300K. The dielectric properties of pure AN were extracted using three different effective medium theories (EMT): (i) the simple effective medium approach, (ii) the Maxwell-Garnett (MG) model, and (iii) the Bruggeman (BR) model. The dielectric properties obtained from theoretical approximations agree well with the experimental values. We identified six lattice vibrational modes between 0.2-3.0 THz that are associated with the polymorphic phase transitions at low temperature.

Paper Details

Date Published: 14 May 2018
PDF: 8 pages
Proc. SPIE 10657, Next-Generation Spectroscopic Technologies XI, 1065714 (14 May 2018); doi: 10.1117/12.2309619
Show Author Affiliations
Abdur Rahman, Edinboro Univ. of Pennsylvania (United States)
David S. Moore, Los Alamos National Lab. (United States)
Abul K. Azad, Los Alamos National Lab. (United States)

Published in SPIE Proceedings Vol. 10657:
Next-Generation Spectroscopic Technologies XI
Mark A. Druy; Richard A. Crocombe; Steven M. Barnett; Luisa T.M. Profeta; Abul K. Azad, Editor(s)

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