Speed-dependent effects and Dicke narrowing in nitrogen-broadened oxygen

•Line shapes of O216 B-band transition were measured.•Self- and N2-broadening line-shape parameters are given.•The hypergeometric and quadratic approximations of the speed-dependent effects are compared.•Line-shape parameters for the quadratic speed-dependent Nelkin-Ghatak profile (SDqNGP) are provided.

We present the line-shape analysis of the nitrogen-broadened P9 P9 oxygen B-band transition measured by the optical frequency comb-assisted Pound-Drever-Hall-locked frequency-stabilized cavity ring-down spectrometer. Perturbation by both oxygen and nitrogen molecules is taken into account simultaneously in the line-shape analysis. Several line-shape models describing physical effects such as Dicke narrowing, the speed dependence of collisional broadening and shifting, and the correlation between velocity- and phase-changing collisions were used in the analysis. The comparison between the hypergeometric and quadratic approximations of the speed-dependent effects is presented. Observed line narrowing is mostly determined by the speed dependence of the collisional broadening.