Terahertz spectroscopy of TNT for explosive detection

Transmittance spectra of solid and vapor samples of trinitrotoluene (TNT) in the spectral range 0.6 to 10 THz at resolutions up to 1 GHz are reported. Uniform solid samples of similar to 100 mu m thickness gave stronger absorption and more resolved structure than previous studies. New absorption lines for TNT solid below 100 cm(-1) are reported. A heated 10 m multpass White cell was used for spectroscopy of the vapor. Strong absorption bands yield unexpectedly large absorption cross sections for the anticipated saturated vapor pressure at the cell temperature, leaving their assignment to TNT in doubt. These results indicate that path lengths exceeding 10 m and temperatures higher than 40 C, or significantly higher instrumental sensitivity, are needed for sensing of TNT vapor in the spectral range 0.6 to 10 TRz.