Measurements and calculations of Kr-broadening and shift parameters of water vapour transitions in a wide spectral region

Abstract

The water vapour line broadening (γ) and shifting (δ) coefficients for 497 lines of 16 vibrational bands ν1, ν3, 2ν2, ν1 + ν2, ν2 + ν3, 3ν2, 2ν2 + ν3, ν1 + 2ν2, ν1 + ν3, 2ν1, 2ν3, 6ν2, 2ν1 + ν2,ν2 + 2ν3, ν1 + 3ν2, and 3ν2 + ν3 induced by krypton pressure were measured with Bruker IFS 125 HR Fourier transform spectrometer. The measurements were performed at room temperature, at the spectral resolution of 0.01 cm−1 and in a wide pressure range of Kr (0.303–0.980 atm). The calculations of the broadening and shift coefficients γ and δ were performed in the framework of the semi-classical method. The intermolecular potential was taken as the sum of the anisotropic atom–atom potential and the vibrationally and rotationally dependent isotropic Lennard-Jones potential. The measured coefficients γ and δ were combined with literature data for the ν2 and rotational bands, and optimal sets of potential parameters that gave the best agreements with the measured broadening coefficients for each vibrational band separately were found. Experimental data for ten vibrational bands of H2O perturbed by Kr were used to determine the analytical dependence of some of the potential parameters on the vibrational quantum numbers. Combined experimental data for the coefficients γ of 19 vibrational bands of H2O perturbed by Kr were fitted to the empirical function. The computed coefficients γ and δ derived from the semi-classical method and the fitted parameters were compared statistically to the measurements. The vibrational dependence of the potential as well as of the coefficients γ and δ is discussed.