Microwave Spectra Of Dinitrotoluene Isomers: A New Step Towards The Detection Of Explosive Vapors

Chrayteh, Mhamad

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https://hdl.handle.net/2142/116685 Copy

Description

Title

Microwave Spectra Of Dinitrotoluene Isomers: A New Step Towards The Detection Of Explosive Vapors

Author(s)

Chrayteh, Mhamad

Contributor(s)

• Cuisset, Arnaud
• Roucou, Anthony
• Goubet, Manuel
• Dréan, Pascal

Issue Date

2022-06-22

Keyword(s)

Large amplitude motions, internal rotation

Abstract

The spectroscopic characterization of explosives taggants, like nitrotoluenes (NT) used for the TNT detection, is a research subject of growing interest. Recently, the spectroscopic studies of the three NT isomers in the microwave and millimeter-wave ranges were reported$^{1,2}$. We present the gas-phase rotational spectroscopic study of weakly volatile dinitrotoluenes (DNT) isomers. The pure rotational spectrum of, 2,4-DNT and 2,6-DNT was recorded in microwave range (2-20 GHz) using a Fabry-Perot Fourier-transform microwave (FP-FTMW) technique coupled to a pulsed supersonic jet. The spectral analysis was supported by quantum chemical calculations carried out at the B98/cc-pvtz and MP2/cc-pvtz levels of theory. The spectra of DNT were complicated by the presence of two $^{14}$N nucleus giving rise to congested hyperfine structures. The methyl group internal rotation barriers were calculated at the B98/cc-pvtz level of theory to be V$_{3}$=563 \wn and V$_{3}$= 696 \wn for 2,4- and 2,6-DNT, respectively. Although no splitting due to internal rotation was observed for 2,6-DNT, several splittings were observed for 2,4-DNT and their analysis in under progress. The semi-rigid and the nuclear quadrupole couplings descriptions obtained from the spectral analysis are presented. An anisotropic internal rotation of the coupled -\chem{CH_3} and -\chem{NO_2} torsional motions, as already mentioned for 2-NT$^{1}$, will be discussed for 2,4-DNT. $^{1}$Roucou et al., CHEMPHYSCHEM, 21, 2523-2538, (2020). $^{2}$Roucou et al., CHEMPHYSCHEM, 19, 1056-1067, (2018). Acknowledgment: This work received financial support from the French Agence Nationale de la Recherche via funding of the project Millimeter-wave Explosive Taggant vapors Investigations using Spectral taxonomy (METIS) under contract number ANR-20-ASTR-0016-03.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

eng

Handle URL

https://hdl.handle.net/2142/116685

DOI

https://doi.org/10.15278/isms.2022.WF04

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Copyright 2022 held by the authors

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