STUDIES OF CO NEAR 4K

Abstract

We have investigated the cooling of CO molecules in collisions with Helium near 4K. In these experiments, warm (300K) CO was injected into Helium gas at 4K. The CO then diffused through the background Helium and condensed on the walls of the container. Temperatures were calculated from a comparison of the linestrengths of several rotational transitions in the millimeter and submillimeter spectral region. Linewidths have been measured and preliminary pressure broadening parameters derived. This is an especially interesting regime in which to study rotational transitions because $kT \approx h\nu$.