Diode laser spectroscopy of methyl chloride near 14 μm toward its detection in the stratosphere

Detection of CHCl in the Earth's atmosphere by infrared techniques is a subject of current interest. The ν band, centered at 732 cm, has lines as strong as those of ν, centered at 2970 cm, and we show that they can be useful for a high-resolution detection. A complete study of the absorption spectrum of this molecule in the region 660-770 cm has been performed. On spectra recorded using a tunable diode laser spectrometer, with the spectral resolution limited by the Doppler width (0.0014 cm), we have assigned the ν band lines related to four isotopic species: CHCl, CHCl, CHCl, and CHCl. In addition, the hot band 2ν - ν for CHCl has been observed. The calculated molecular constants reproduce, for each band, the observed wavenumbers with a rms deviation of 6 × 10 cm. The ν band centers have been found to be 732.8421 and 727.0295 cm for the two main isotopic species, CHCl and CHCl, respectively. The feasibility of detection of methyl chloride in the stratosphere is discussed.