A bond-bond description of the intermolecular interaction energy: The case of the weakly bound acetylene-hydrogen complex

A new semiempirical potential energy surface (PES) for the acetylene-hydrogen system has been derived by using the recently introduced bond-bond methodology. The proposed PES, expressed in an analytic form suitable for molecular dynamics simulations, involves a limited number of parameters, each one having a physical meaning and allowing the accurate description of the system also in the less stable configurations. The analysis of novel integral cross sections data, measured with nearly effusive molecular beams, combined with that of available pressure broadening coefficients of isotropic Raman lines at 143 K and IR lines at 173 and 295 K of C2H2 in H 2, provides a test of the reliability of the proposed PES and suggests also some refinements. An extensive comparison with a recent ab initio potential is also exploited. © 2009 American Chemical Society.The work in Perugia has been supported by the Italian Ministero della Universita´ e Ricerca (MIUR) through the PRIN programme. M.B. was supported by the “JAEdoc” programme of Consejo Superior de Investigaciones Cientı´ficas and by the Ministerio de Educacio´n y Ciencia (Spain, Grant CTQ 2007-62898-BQU).Peer Reviewe