Knowledge Bank

Pressure broadening and line shift cross sections for the 1$\leftarrow$0and2$\leftarrow$1 rotational transitions of carbon monoxide (CO) in collision with Helium (He) have been measured between 1 and 600 K. Measurements below 30 K were made using the collisional cooling technique, while measurements at higher temperatures were made in an equilibrium cell. The experimental apparatus and techniques employed in the study are described. The data are compared with theoretical predictions, and the significant differences between predictions based on the best available potential energy surface and the experimental results are discussed. Recent studies of the pressure broadening and line shifting of the $110\leftarrow 111$ rotational transition of deuterated water (HDO) in collision with He will also be presented.