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

Phys Chem Chem Phys. 2008 Sep 21;10(35):5419-28. doi: 10.1039/b804306j. Epub 2008 Jul 9.

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 acetylene nu2 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.