ABSTRACT
Introduction It is well known that dense gases of infrared inactive molecules such as H2 absorb infrared radiation. Absorption continua range from the microwave and far infrared regions of the spectrum to the near infrared and possibly into the visible. Collisionally interacting pairs of hydrogen molecules possess transient electric dipole moments, which are responsible for the observed absorption continua [1, 2]. Planetary scientists understood early on the signicance of collision-induced absorption (CIA) for the modeling of the atmospheres of the outer planets [3, 4]. More recently, it was shown that the emission spectrum of cool white dwarf stars diers signicantly from the expected blackbody spectrum of their cores: CIA in the dense helium and hydrogen atmospheres suppresses (lters) the infrared emissions strongly [5-10]. Detailed modelling of the atmospheres of cool stars with proper accounting for the collision-induced opacities is desirable, but it has been hampered heretofore by the highly incomplete or nonexisting theoretical and experimental data on such opacities at temperatures of many thousands of kelvin.
