15min:

MARTIN ABEL, LOTHAR FROMMHOLD, Department of Physics, The University of Texas at Austin, Austin, TX 78712; XIAOPING LI, KATHARINE L. C. HUNT, Department of Chemistry, Michigan State University, East Lansing, MI 48824.

The interaction-induced absorption by collisional pairs of H₂ molecules is an important opacity source in the atmospheres of the outer planets and cool stars . 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 H₂--H₂, H₂--He, and H₂--H complexes in the stellar atmospheres. Using quantum-chemical methods we compute the atmospheric absorption from hundreds to thousands of kelvin . Laboratory measurements of interaction-induced absorption spectra by H₂ pairs exist only at room temperature and below. We show that our results reproduce these measurements closely , so that our computational data permit reliable modeling of stellar atmosphere opacities even for the higher temperatures .