Line-by-line measurements of interference parameters for the 0–1 and 0–2 bands of CO in He, and comparison with coupled-states calculations

Here we present the first line-by-line measurements of interference parameters Y0k describing line-mixing effects in the weak overlapping regime for He-broadened CO lines in the 0–1 and 0–2 bands at 296 K. A detailed analysis of the line shape at intermediate perturber pressures (up to about 10 atm) has been performed, starting from previous theoretical calculations, which has demonstrated the possibility of an individual measurement of Yk parameters. The method is based on the existence of a component of the line shift, quadratic with the perturber pressure (density) and proportional to Y0k. Comparison of our measurements with results predicted from coupled-states calculations shows good overall agreement. Linear pressure shifts have also been simultaneously measured. The uncertainty on the data is important since linear shifts are very small; however, some features can be considered as significant although we have no clear understanding of them. Possible explanations are discussed.