Detection and identification of substance (explosive, drugs) using the dynamics of spectral lines distorted by influence of ambient medium

Abstract

Some of the modern problems arising in the detection and identification of substances are an influence of water vapor and opaque coverings and surface of the explosive and an influence of ambient medium (for example, atmospheric gases) on the THz signal reflected from the sample. All influencing factors mentioned above distort the signal and its spectrum. Therefore, we get the signal with information about the ambient medium and coverings. We show in this paper that the method of the spectral dynamics analysis (SDA-method) is convenient tool for the detection and identification of the explosive and drugs at such conditions. For this aim we develop the method which allows us to get the dynamics of spectral lines of the explosive response distorted by action of various causes. We compare the new method of finding the spectral lines dynamics with previous method based on FTST (Fourier-Gabor transform). It is essential that we analyze the THz pulse with a few cycles. As consequence, this pulse has a broad spectrum. To remove the action of opaque coverings it is sufficient to analyze the sub-pulse which follows after reflected main pulse. To avoid an influence of water vapor it is sufficient to use the transparent windows of atmosphere. We show the possibility to get the dynamics of spectral lines without its distortion by neighboring frequencies under certain choice of both the order of measurements and time window for the computer processing of the signal reflected from the sample. Analysis of the spectral line dynamics allows us to avoid the influence of surface of the explosive on the detection and identification of forbidden substance as we believe. This problem requires additional investigations. Nevertheless, the preliminary results of investigations show the validity of such approach to get true way.