Line broadening and line shift of H2S absorption lines in the v(2) 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 bi nary (H2S-H2O, H2S-Ar) and three-component mixtures (H2S-Ar-H2O) were measu red using a high-resolution diode-laser spectrometer with a spectral resolu tion better than 5 x 10(-4) cm(-1) and two multipass Herriott absorption ce lls. The measurements were carried out to check experimentally the additivi ty of the binary collisions contributions to the broadening and shift of th e same absorption line in the mixture of H2S-Ar-H2O. Due to the atmospheric relevance as one collisional partner water vapor was selected. The mixture s 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 varie d 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 c oefficient delta were measured to be: gamma (H2S-H2O) = (0.265 +/- 0.001) c m(-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 th e H2S-H2O and H2S-Ar shift coefficients could be proved with an averaged de viation less than 13% which is comparable to the uncertainty of the shift m easurements, (C) 2001 Published by Elsevier Science Ltd.