Knowledge Bank

Low temperature studies of the pressure-broadening of infrared lines is limited by the smallness of the vapor pressure of most compounds when cooled, resulting in an absorption spectrum made of sharp lines, whose widths are difficult to measure. The very high resolution of the tunable diode lasers makes this kind of measurements feasible. Using a newly designed liquid-nitrogen-cooled absorption cell, the collision-broadening of $CO(v=1\leftarrow 0)$ infrared lines has been investigated, when perturbed by molecular $H2$ and the light noble gases He, Ne. $CO-H2$ results will be discussed in connection to previous double resonance measurements and calculations of inelastic cross $sections(1)$, as well as astrophysical implications. CO-He results will be compared to the cross sections derived from a recently obtained high accuracy ab initio potential energy $surface(2)$ by close-coupling calculations.