Temperature-Dependent Far-Infrared Spectra of Single Crystals of High Explosives Using Terahertz Time-Domain Spectroscopy

Barber, Jeffrey; Hooks, D. E.; Funk, David J.; Averitt, R. D.; Taylor, Antoinette J.; Babikov, Dmitri

doi:10.1021/jp044384h

Cited by 85 publications

(62 citation statements)

References 12 publications

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“…7͒ and TNT, 1,5,6 and a THz measurement of a single RDX crystal. 9 The pellet samples in these previous works were formed under pressure from a mixture of the explosive powder diluted in a transparent polyethylene matrix. The top panels of Figs.…”

Section: 13mentioning

confidence: 99%

“…7͒ and TNT pellet samples 1,5,6 and RDX single crystal. 9 This comparison emphasizes the much sharper absorption features and much more informative vibrational spectra provided by the waveguide film when cooled to near 10 K. For example, the relatively broad room temperature absorption at 1.06 THz of the RDX Al waveguide film with an FWHM linewidth estimated to be approximately 0.12 THz ͑Ref. 20͒ narrows by more than an order of magnitude when the film is cooled to 13 K, producing a blueshifted line at 1.276 THz with a FWHM linewidth of 9 GHz ͑Table I͒.…”

Section: 13mentioning

confidence: 99%

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The underlying terahertz vibrational spectrum of explosives solids

Melinger

Laman

Grischkowsky

2008

Applied Physics Letters

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Using waveguide terahertz time-domain spectroscopy, we demonstrate the measurement of the underlying terahertz vibrational spectrum of the explosive solids hexahydro-1,3,5-trinitro-1,3,5-triazine, and 2,4,6-trinitrotoluene. Each explosive is cast as a polycrystalline thin film with planar ordering on the inner surface of metal parallel plate waveguide. For measurements near 10 K, each explosive reveals a complex spectrum of approximately 20 vibrational modes between 0.5 and 3.5 THz. The explosive films are of sufficient quality to produce vibrational linewidths as much as an order of magnitude sharper compared to conventional terahertz measurements of corresponding pellet samples of explosives. © 2008 American Institute of Physics. ͓DOI: 10.1063/1.2949068͔One of the most promising and discussed applications of terahertz ͑THz͒ spectroscopy is the detection and identification of explosive materials.1-3 Previous work has measured the THz absorption of explosive solids, revealing a number of broad features associated with the signature vibrational modes of the material.1,2,4-9 However, the majority of this work has been performed on disordered polycrystalline pellet samples, 1,2,4-8 resulting in inhomogeneous broadening of the absorption features, making their identification more difficult. We have addressed this problem by developing the technique of waveguide terahertz time-domain spectroscopy ͑THz-TDS͒, 10,11 whereby an ordered polycrystalline film is formed on a metal surface and its THz vibrational response is characterized via a parallel plate waveguide ͑PPWG͒. 12,13The planar order of the sample together with the formation of microcrystals of high crystalline quality reduces the inhomogeneous broadening, resulting in considerably sharper and much more identifiable features.11,14-18 Here, we present the application of waveguide THz-TDS to the explosive solids hexahydro-1,3,5-trinitro-1,3,5-triazine ͑RDX͒ and 2,4,6-trinitrotoluene ͑TNT͒, resulting in a dramatic sharpening of the vibrational absorption lines as the films are cooled to near 10 K. The linewidths measured at their full width at half maximum ͑FWHM͒ by waveguide THz-TDS are in some cases more than an order of magnitude sharper than corresponding THz measurements with standard pellets of explosives, and reveal a rich spectrum of approximately 20 narrow vibrational absorption lines between 0.5 and 3.5 THz. This information can provide an extraordinary precise "spectral fingerprint" capable of identification by a series of unique vibrational absorption lines. Such narrow vibrational lines can also provide rigorous input to help guide theoretical modeling 19 and advance the understanding of the vibrational properties of explosive solids.The THz measurement apparatus, method for the recovery of absorbance spectra for the waveguide films, and details of the PPWG have been described previously in Refs. 11 and 14. Prior to film formation, the metal waveguide plates were thoroughly washed with solvent and then plasma cleaned. Thin films of RDX and TNT were fo...

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Section: 13mentioning

confidence: 99%

Section: 13mentioning

confidence: 99%

The underlying terahertz vibrational spectrum of explosives solids

Melinger

Laman

Grischkowsky

2008

Applied Physics Letters

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“…Specifically, the ability to perform imaging in the THz would have profound impact on the areas of security [1,2,3,4], biology [5,6], and chemistry [7,8]. However, imaging in the terahertz is complicated by the a lack of easily accessible electromagnetic responses from naturally occurring materials.…”

Section: Introductionmentioning

confidence: 99%

Design, theory, and measurement of a polarization-insensitive absorber for terahertz imaging

et al. 2009

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“…One of the driving forces behind the development of the terahertz technique (the spectral range from 0.1 to 10 THz) is the fact that many commonly used explosive materials (such as RDX, PETN, HMX, TNT and NQ) have unique spectral features in this range of radiation [6][7][8][9][10][11][12][13][14][15][16][17][18][19]. Moreover, non-polar dielectric materials (such as clothes, paper and plastics) are relatively transparent in the range up to about 3 THz [6,9], which raises hope of efficient identification of explosive materials remaining under cover or being inside packaging [6,12].…”

Section: Introductionmentioning

confidence: 99%

“…Most of the mentioned explosive materials have been thoroughly investigated in transmission [6-8, 13, 16] and in reflection configurations [7,13]. Experiments have been carried out in different temperatures [14]; also, solid-state density functional theory calculations have been performed [15]. Methods for identifying explosive materials by means of their spectra are constantly being developed [16][17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Transmission and Reflection Terahertz Spectroscopy of Insensitive Melt-Cast High-Explosive Materials

Pałka

Szala

2016

J Infrared Milli Terahz Waves

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Currently, artillery shells and grenades that are introduced into the market are based on melt-castable insensitive high explosives (IHEs), which do not explode while they run a risk of impact, heat or shrapnel. Particles of explosives (such as hexogen, nitroguanidine and nitrotriazolone) are suspended in different proportions in a matrix of 2.4-dinitroanisole. In this paper, we investigated samples of commonly used IHEs: PAX-41, IMX-104 and IMX-101, whose internal structures were determined by a scanning electron microscope. Terahertz time domain spectroscopy was applied in both transmission and reflection configurations. At first, the complex refraction indices of four pure constituents creating IHEs were determined and became the basis of further calculations. Next, the experimentally determined transmission and reflection spectra of IHEs and pure constituents were compared with theoretical considerations. The influence of the grain size of constituent material and scattering on the reflection spectra was analysed, and good agreement between the experimental and theoretical data was achieved.

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Temperature-Dependent Far-Infrared Spectra of Single Crystals of High Explosives Using Terahertz Time-Domain Spectroscopy

Cited by 85 publications

References 12 publications

The underlying terahertz vibrational spectrum of explosives solids

The underlying terahertz vibrational spectrum of explosives solids

Design, theory, and measurement of a polarization-insensitive absorber for terahertz imaging

Transmission and Reflection Terahertz Spectroscopy of Insensitive Melt-Cast High-Explosive Materials

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