Line broadening and line shift of H2S absorption lines in the v2 band -: collisions with H2O and Ar in a three component mixture

Lorentzian half-widths (HWHM) and shifts of the H2S absorption line at 1294.5083 cm(-1) (upsilon (2) band) induced by the pressure of H2O and Ar in binary (H2S-H2O, H2S-Ar) and three-component mixtures (H2S-Ar-H2O) were measured using a high-resolution diode-laser spectrometer with a spectral resolution better than 5 x 10(-4) cm(-1) and two multipass Herriott absorption cells. The measurements were carried out to check experimentally the additivity of the binary collisions contributions to the broadening and shift of the same absorption line in the mixture of H2S-Ar-H2O. Due to the atmospheric relevance as one collisional partner water vapor was selected. The mixtures of H2S-H2O-Ar were prepared with a fixed partial pressure of H2S and Ar. The H2S pressure was selected to about 2 Torr, the Argon pressure was varied between 2.3 and 6.3 Torr, whereas the H2O pressure varied from 0 till 12 Torr, The averaged H2S-H2O, H2S-Ar broadening coefficient gamma and shift coefficient delta were measured to be: gamma (H2S-H2O) = (0.265 +/- 0.001) cm(-1)/atm, delta (H2S-H2O) = + (0.016 +/- 0.001) cm(-1)/atm, delta (H2S-Ar) = (0.0381 +/- 0.0002) cm(-1)/atm, and delta (H2S-Ar) = -(0.0016 +/- 0.0001) cm(-1)/atm. Additivity concerning broadening was found to be proved with a deviation less than 1.3%. Concerning the line shift it is shown that fur mixtures H2S-Ar-H2O with pressures larger than 10 Torr the additivity of the H2S-H2O and H2S-Ar shift coefficients could be proved with an averaged deviation less than 13% which is comparable to the uncertainty of the shift measurements, (C) 2001 Published by Elsevier Science Ltd.