Linewidths of C2H2 perturbed by H2: experiments and calculations from an ab initio potential

Abstract

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-coupling approach and the coupled-states approximation, pressure broadening coefficients of C₂H₂ isotropic Raman Q lines over a temperature range of 77 to 2000 K. Experimental data for the acetyleneν₂ Raman lines broadened by molecular hydrogen are obtained using stimulated Raman spectroscopy. The comparison of theoretical values with experimental data at 143 K is promising. Approximations to increase the computational efficiency are proposed.