Collision-induced rototranslational spectra ofH2-He from an accurateabinitiodipole moment surface

Abstract

For the study of collision-induced dipole moments, the collisional ${\mathrm{H}}_2$-He complex is treated as a molecule in the self-consistent-field and size-consistent coupled electron pair approximations. The basis set accounts for 95% of the correlation energies and separates correctly at distant range. The vibrational average (v=v’=0) of the induced dipole components is obtained and recast in a simple but accurate analytical representation. It is used for computations of the spectral moments and spectral profile of the collision-induced rototranslational spectra of ${\mathrm{H}}_2$-He. The computations are in close agreement, on an absolute intensity scale, with Birnbaum’s measurements at 77, 195, and 292 K of such spectra. The fundamental theory is thus seen to predict these spectra reliably even when the anisotropy of the potential is neglected, probably with an accuracy of better than 5%, over the frequency band from 0 to ∼2000 ${\mathrm{cm}}^{\mathrm{-}1}$.