Line mixing in the oxygen B band head.

We present the results of direct measurements of the line mixing parameters for two pairs of overlapping transitions at the band head of the oxygen B band. Measurements were performed with the frequency-stabilized cavity ring-down spectrometer assisted by an optical frequency comb. The recorded spectra were analyzed with line profiles comprising speed dependence, Dicke narrowing, and line mixing. Incorporation of the line mixing into the model eliminated previous discrepancies for pressure shift and their speed dependence coefficients. First-order line mixing was determined directly from the line shape fitting at relatively low pressure (0.04 atm) together with other line shape parameters and compared with that calculated by Sung et al. [J. Quant. Spectrosc. Radiat. Transfer 235, 232-243 (2019)].