Halogenated hydrocarbon gas sensing by rotational absorption spectroscopy in the 220–330 GHz frequency range

Gas sensing for halogenated hydrocarbons is demonstrated using rotational absorption spectroscopy in the 220–330 GHz frequency range, carried out with a compact and robust broadband microelectronics-based THz-wave spectrometer. Monitoring of halogenated hydrocarbons is necessary in industrial situations where these chemicals present a danger to human health and the environment, due to their toxicity, volatility, and reactivity. The absorption spectra for pure chloromethane, dichloromethane, chloroform, iodomethane, and dibromomethane were characterized at 297 K and pressures from 0.25 to 16 Torr. The spectra show the unique rotational fingerprints for the target halogenated hydrocarbons in the 220–330 GHz frequency range and demonstrate the potential for their selective quantitative detection in gas sensing applications with minimum detection for pure gases of order 1012–1013 molecules/cm3 and for dilute gases of order 10–100 ppm at 1 atm for a 1 m pathlength. The study further demonstrates the potential of all-electronic miniaturized THz-wave gas sensors.