Collision‐induced absorption at temperatures of thousands of kelvin, from first principles, for astrophysical applications

New ab initio surfaces of the potential energies and the induced electric dipole moments of H2–H2 and H2–He collisional complexes are obtained with H2 bond distances from 0.942 to 2.801 bohr. These data permit the calculation of collision-induced absorption (CIA) spectra of dense hydrogen-helium gas mixtures at temperatures up to thousands of kelvin, i.e., under conditions where strong rotovibrational excitations of the H2 molecules exist. First results of CIA spectra are obtained over an extended range of frequencies and temperatures. The work is an extension of our previous work on the opacities of the (low-temperature) atmospheres of the outer planets.