Terahertz time-domain spectroscopy characterization of nitrocellulose in transmission and reflection configurations

In this work, we report the first terahertz characterization of nitrocellulose, a workhorse energetic material widely employed in many civilian and military applications, especially as a propellant or explosive ingredient. The aim behind this study is to find the main spectral features and to draw the absorption and refractive index profiles of nitrocellulose using a terahertz time-domain spectroscopy setup over the frequency range from 0.3 to 3 THz. We particularly highlight the interest of carrying out combined measurements in transmission and in reflection configurations in order to increase the identification capabilities using the terahertz spectroscopy. Thus, five spectral absorption lines have been clearly observed in transmission mode, namely 0.41, 0.69, 1.01, 2.15 and 2.76 THz. These spectral resonances constitute fingerprints of nitrocellulose. When spreading a few particles of NC on an adhesive ribbon and performing characterization in reflection, the lines at 0.69 and 2.15 THz are still easily observed. These spectral fingerprints allow a simple, easy and highly sensitive remote detection and identification of nitrocellulose even if it is concealed behind barrier materials like papers, textiles and so forth.