A spectroscopic study of water vapor isotopologues H216O, H218O and HDO using a continuous wave DFB quantum cascade laser in the 6.7 μm region for atmospheric applications

A quantum cascade spectrometer was used in the laboratory to study H216O, H218O and HDO line intensities near 6.7 μm. The spectral region ranging from 1483 to 1487 cm−1, which is suitable for the in situ laser sensing of these isotopologues in the atmosphere, was investigated using a continuous-wave distributed feed-back quantum cascade laser. Eight lines of water vapor isopologues were studied-one line of the ν2 band of H216O, one line of the 2ν2-ν2 band of H216O, two lines of the ν2 band of H218O and four lines of the ν2 band of HDO were carefully revisited. The measured intensities were thoroughly compared to relevant molecular databases and other experimental and calculated results. We also observe that the H2O, D2O, HDO equilibrium constant agrees excellently with previously determined values.