Terahertz time-domain spectroscopy, imaging and density functional theory based studies of 3, 4, 5 Trinitro 1 H Pyrazole

Abstract

The paper reports the terahertz time-domain spectroscopy (THz-TDS) and imaging on 3, 4, 5 -Trinitro 1-H Pyrazole (explosive) in solid form between 0.1 and 3.5 THz range, including Density Functional Theory was implemented in this study. We have employed a commercially available fiber-coupled THz reflection mode system. We have experimentally ascertained the optical and dielectric properties such as refractive index, absorption coefficients, and dielectric constants in the THz domain. The refractive index values varies between 1.5 and 2.0 range, and absorption coefficients varies between 10 and 400 cm−1 in the stated THz range. In addition, Density Functional Theory was used to assign some important vibrational modes obtained experimentally. In the next step, the Dimer and Trimer configurations of the molecule were also incorporated in the existing theoretical model for developing a clear-cut understanding the role of the intermolecular vibrational modes in the molecule. The simulated results were compared in the IR region (4000–400 cm−1) and the THz region (0.1–3.5 THz). Finally, an improvised version of the imaging system was used to record the THz time and frequency domain images of pure pyrazole and mixed in a teflon matrix with different concentrations. The spatial distributions of pyrazole in the pure and teflon matrix at different absorption frequencies have been analysed.