Experimental meaurements in phase gas and theoritical analysis in the THz and InfraRed domains of explosives compounds – MEGATHIREX

Improvised explosive devices (IED), also known as roadside bombs are causing increased losses of troops and are also widely used for terrorist attacks too. Such devices use various kinds of explosives and due to the difficulty to detect them they are extremely effective.
A large range of detection solutions are being evaluated. Optical spectroscopy techniques have without doubt great potential. Among this panel, we propose to use THz radiation, located between the microwaves and infrared bands.
THz Spectroscopy is an excellent alternative completing or even to improve traditional approaches for the detection pyrotechnic compounds. Indeed, THz spectroscopy is characterized by an excellent molecular selectivity, with rotational lines of small polar molecules and/or low frequency vibrational signatures of bigger molecular systems. THz spectroscopy is a breakthrough technique for detection, analysis and quantification of a wide variety of molecular compounds . The potentiality of this technique is considered in the context of the detection of chemical agents involved in military programs.
While gases has been studied for a long time in the THz domain for fundamental science, the interaction of the THz radiation with explosives substances has only recently been started to be examined. THz Time Domain Spectroscopy (THz TDS) has removed many technological difficulties to initiate those first studies in this spectral gap. Now, many data are available on these types of compounds. However the data contain substantial discrepancies probably due to various experimental conditions measurements (pure or diluted, the use of matrix or not…). Moreover, the additives can modify and so complicate the recognition of prohibited substance present in a mixture. We can also legitimately question the feasibility of identifying an individual compounds whien its spectrum is not attributed to any isolated spectral lines.

Some explosives and their derivatives have significant vapour pressure which can be use for the detection with a high degree of discrimination. However, these relatively heavy compounds are not very volatile, and therefore require very high sensitivity spectrometers, especially as additives further decrease their volatility. Such approaches have great potential, but require an extensive and fundamental study of the spectral signatures. To the best of our knowledge, THz gas phase spectra of the most volatile explosives are not available.

The objective of this proposal is to record and fully interpret the THz and Far Infrared spectra of the vapour pressures of some target explosives and /or their derivative compounds. Without doubt, these new data provide information about the potential of this spectral band to detect such substances in the gas phase. So, the industrial partner will propose several approaches towards studies or experimental development at higher TRL levels.