Knowledge Bank

A new system has been developed which has allowed us to measure the hydrogen pressure broadening parameters of $CO,CH3F$, and $H2S$ between approximately 5K and 100K. In combination with other experimental systems, this has allowed measurements over the entire 5K to 1000K range, In the semiclassical region above -100K, the behavior of the cross sections for collisions with hydrogen is more complex than comparable collisions with helium because of the additional rotational degrees of freedom in the hydrogen molecule. At low temperatures very significant increases in cross section, which are associated with the quasibound states, are observed. The new apparatus, which is particularly simple, will be described as will experimental results and their relationship to theoretical predictions. Similarities and differences with the results of helium pressure broadening work discussed in the previous talk will be presented.