Gas sensing for industrial relevant nitrogen-containing compounds using a microelectronics-based absorption spectrometer in the 220–330 GHz frequency range

Gas sensing for four nitrogen-containing compounds (nitrous oxide, acetonitrile, nitric acid, and nitromethane) is explored and demonstrated using rotational absorption spectroscopy carried out with a compact terahertz-wave microelectronics-based spectrometer operating in the 220–330 GHz frequency range. The four gases investigated are important in industrial processes, as well as in chemical, combustion, environmental, and agricultural contexts. Absorption measurements were made at room temperature (297 K) and moderate pressures (33.3–2133 Pa or 0.25–16 Torr) for the characterization of spectra that are comprised of distinct fingerprint features that include isolated single transitions and bands of pressure-broadened transitions, emanating from both ground vibrational states, as well as low-lying vibrationally-excited states. The measurements demonstrate that terahertz-wave quantitative gas sensing using all-electronic miniaturized systems is possible for nitrogen-containing compounds with detection limits of the order 1012-1013 molecules cm−3 per meter pathlength and for dilute gases in air at 1 atm at concentrations of 5–1000 ppm per meter pathlength.