Collision-Induced Absorption by Supermolecular Complexes from a New Potential Energy and Induced Dipole Surface, Suited for Calculations up to Thousands of Kelvin

Abstract

Absorption by pairs of H2 molecules is an important opacity source in the atmospheres of the outer planets, and thus of special astronomical interest. The emission spectra of cool white dwarf stars differ significantly from the expected blackbody spectra, amongst other reasons due to absorption by H2‐H2, H2‐He, and H2‐H collisional complexes in the stellar atmospheres. To model the radiative processes in these atmospheres, which have temperatures of several thousand kelvin, one needs accurate knowledge of the induced dipole (ID) and potential energy surfaces (PES) of such collisional complexes. These come from quantum‐chemical calculations with the H2 bonds stretched or compressed far from equilibrium. Laboratory measurements of collision‐induced (CI) absorption exist only at much lower temperature. For H2 pairs at room temperature, the calculated spectra of the rototranslational band, the fundamental band, and the first overtone match the experimental data very well. In addition, with the newly obtained ...