Collision-Induced Infrared Absorption by Hydrogen-Helium gas mixtures at Thousands of Kelvin*

The interaction-induced absorption by collisional pairs of H$_{2}$ molecules is an important opacity source in the atmospheres of the outer planets and cool stars $^{[1]}$. The emission spectra of cool white dwarf stars differ significantly in the infrared from the expected blackbody spectra of their cores, which is largely due to absorption by collisional H$_{2}$--H$_{2}$, H$_{2}$--He, and H$_{2}$--H complexes in the stellar atmospheres. Using quantum-chemical methods we compute the atmospheric absorption from hundreds to thousands of kelvin $^{[2]}$. Laboratory measurements of interaction-induced absorption spectra by H$_{2}$ pairs exist only at room temperature and below. We show that our results reproduce these measurements closely $^{[2]}$, so that our computational data permit reliable modeling of stellar atmosphere opacities even for the higher temperatures $^{[2]}$. [1] L. Frommhold, Collision-Induced Absorption in Gases, Cambridge University Press, Cambridge, New York, 1993 and 2006 [2] Xiaoping Li, Katharine L. C. Hunt, Fei Wang, Martin Abel, and Lothar Frommhold, ``Collision-Induced Infrared Absorption by Molecular Hydrogen Pairs at Thousands of Kelvin'', International Journal of Spectroscopy, vol. 2010, Article ID 371201, 11 pages, 2010. doi: 10.1155/2010/371201