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 10(12)-10(13) molecules/cm(3) 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.