Measurement and analysis of rotational lines in the (2ν1 + ν2 + ν3) overtone band of H2O perturbed by CO2 using near infrared diode laser spectroscopy

We report the CO2-induced broadening coefficients and line strength parameters of water vapor rovibrational transitions belonging to the (2ν1 + ν2 + ν3) overtone band measured by using an NIR diode laser spectrometer. Rotational quantum number dependence of the broadening coefficients is also shown. Use of balanced photodetector and wavelength modulation spectroscopy with small current modulation amplitude helped to obtain improved S/N ratio of the spectra. The recorded line shapes are fitted with standard Voigt profile by using a non-linear least squares fitting program to extract the line shape parameters.