Intermolecular interaction in the H2S-H2 complex: molecular beam scattering experiments and ab-inito calculations

New molecular beam scattering experiments are reported for the H2S-H2 system recording, under high angular and velocity resolution conditions, the "glory" quantum interference in the velocity dependence of the total cross section. The analysis of the experimental data permits the determination, for the first time, of a spherically averaged intermolecular potential for this system. An evaluation of significant cuts of the potential energy surface, obtained by accurate ab initio CCSD(T) calculations using large basis sets, combined with the analysis of the electronic charge displacement accompanying the formation of H2S-H2, has been also performed in order to rationalize the experimental findings. A direct comparison with the analogous water-hydrogen complex (Belpassi, L. et al. J. Am. Chem. Soc. 2010, 132, 13046), investigated with the same experimental conditions and theoretical methodology, brings to light detailed differences in the intermolecular interaction affecting the observables. In particular, it shows the important fact that the charge transfer (CT) component of the interaction plays a minor role in H2S-H2, whereas it was found to be a crucial stabilization component of the interaction in water-H2, determining the potential energy surface anisotropy and the precise location of the energy minima.