In this work we present a theoretical and experimental study of the acetylene -hydrogen system.A potential surface considering rigid monomers has been obtained by ab initio quantum chemistry methods. This 4-dimensional potential is further employed to compute using the close-clouping approach and the coupled-states approximation pressure broadening coefficients of C 2 H 2 isotropic Raman Q lines over a temperature range of 77 to 2000 K. Experimental data for the acetylene ν 2 Raman lines broadened by molecular hydrogen are obtained using stimulated Raman spectroscopy.The comparison at 143 K of theoretical values with experimental data is promising. Approximations to increase computational efficiency are proposed. *

We present measurements of Raman linewidths in the fundamental Q branch of CO for mixtures with Ar at temperatures of 77, 195, and 300 K, recorded using an inverse Raman spectrometer. Starting from a recent ab initio potential energy surface, theoretical values of Ar broadening coefficients for CO infrared and Raman lines (isotropic and anisotropic components) at temperatures in the range 77 to 1100 K are calculated via quantum-mechanical methods. The relative merits of the close coupling theoretical results over the coupled states results are underlined. Finally, a comparison of the calculated pressure broadening coefficients is made with the present experimental data as well as with recently available infrared data. There is general agreement between the calculated and measured values of the broadenings for all the temperatures probed. We conclude that the temperature dependence of the infrared and Raman broadening coefficients have been correctly determined theoretically and may be used to test a common temperature scaling law.

This work presents a comparison between experimental and calculated values for the collisional line broadenings and shifts of the S0(0), S0(1), and S0(2) lines of the rotational Raman spectrum of D2 perturbed by He at 77, 195, and 300 K. The pure rotational Raman spectra were obtained by means of a stimulated Raman spectroscopy experimental setup. Close coupling dynamical calculations were performed on the most recent ab initio H2–He potential energy surface. The resulting scattering matrix elements implemented in the general Hess method allow us to provide pressure broadening, pressure shifting, and Dicke coefficients from 10 to 400 K. Experimental and calculated values agree well with each other.

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