Temperature-dependent far-infrared spectra of single crystals of high explosives using terahertz time-domain spectroscopy

Survey spectra of single-crystal HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7- tetrazocine), RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine), and PETN (pentaerythritol tetranitrate) were acquired in the region from 10 to 80 cm ^-1 using terahertz time-domain spectroscopy. The spectra were taken at temperatures ranging from 8.4 to 300 K. Generally, the spectra show multiple absorption peaks in the range 50-80 cm ^-1, with PETN (110) showing strong absorption features at room temperature. RDX (210) is the most notable in the region 10-40 cm ^-1, showing multiple spectral features, while HMX (010) shows a very broad absorption at 47.8 cm ^-1 with a fwhm of 37.3 cm ^-1. Future plans include polarization-dependent investigations for multiple crystallographic orientations over an increased spectral range and higher-level theoretical calculations.