Spectral line shapes of P-branch transitions of oxygen B-band

The precise line-shape measurements of self- and foreign-broadened P-branch transitions of the oxygen B band near 689 nm are presented. Data were obtained using the Pound–Drever–Hall-locked frequency-stabilized cavity ring-down spectrometer assisted by the optical frequency comb.^1,2 This technique enables us to achieve high spectral resolution (about 1 MHz) and high signal-to-noise ratio spectra (above 10000:1) of weak transitions.^3,4 It is showed that the inclusion of the line-narrowing effects (Dicke narrowing or the speed dependence of collisional broadening) is necessary to properly model measured line shapes. The multispectrum fitting technique is used to minimize correlation between line-shape parameters. Relations between the line narrowing obtained from different line-shape models in the low pressure limit (below 5 kPa) were verified experimentally. Line positions with uncertainties of about 170 kHz, intensities and the collisional broadening coefficients with uncertainties of about 0.5% are reported and compared to data available in the literature.⁵

The research is part of the program of the National Laboratory FAMO in Toruń, Poland, and is supported by the Polish National Science Centre Projects no. DEC-2011/01/B/ST2/00491 and UMO-2012/05/N/ST2/02717. The research is also supported by the Foundation for Polish Science TEAM and HOMING PLUS Projects co-financed by the EU European Regional Development Fund. A. Cygan is partially supported by the Foundation for Polish Science START Project.