Anisotropic interactions of hydrogen molecules from the pressure dependence of the rotational spectrum in the Ar(H-2)(2) compound - art. no. 125506

We report the pressure evolution, up to 70 GPa, of the fine structure of th e S-0(0) rotational excitation in the high-pressure Ar(H-2)(2) compound (wi th almost 100% para-H-2) at about 30 K. A perturbative theoretical analysis is developed to calculate intensities and frequency shifts of the active R aman rotational components, on the basis of the intermolecular anisotropic interaction. The comparison between experimental results up to 35 GPa and c alculation allows a reliable determination of the anisotropic intermolecula r potential in the solid, both for H-2-H-2 and H-2-Ar at short range. Such results are important for the interpretation of the high-pressure orientati onal properties of solid hydrogen.