High resolution THz spectroscopy of ammonium nitrate and potassium nitrate crystalline films

We have performed high resolution terahertz vibrational spectroscopy of ammonium nitrate and potassium nitrate crystalline films and their mixtures employing waveguide terahertz time domain spectroscopy. Measurements were conducted on films that were drop cast from solution onto aluminum and gold surfaces. The terahertz spectra of the films were compared with more traditional terahertz time domain measurements of ammonium nitrate and potassium nitrate pellets. Temperature dependence studies indicate that as samples were cooled to cryogenic temperatures the vibrational lines become significantly narrower and more intense, more so in the case of films than pellets. We also investigate line broadening caused by impurities by measuring terahertz spectra ammonium films containing small amounts of potassium nitrate.