High accuracy spectroscopic parameters of the 1.27 µm band of O2 measured with comb-referenced, cavity ring-down spectroscopy

• Published in: Journal of quantitative spectroscopy & radiative transfer 2021-08, Vol.270, p.107684, Article 107684
• Main Authors: Fleurbaey, Hélène, Reed, Zachary D., Adkins, Erin M., Long, David A., Hodges, Joseph T.
• Format: Article
• Language: English
• Subjects: Cavity ring-down spectroscopy; Collisional induced absorption; Hartmann-Tran profile; Line intensity; Line shape parameters
• ISSN: 0022-4073; 1879-1352
• DOI: 10.1016/j.jqsrt.2021.107684

•High-precision, low-uncertainty CRDS measurements of 1.27 µm air-broadened O2 band line with frequency axis linked to Cs clock.•New line list reported using Dicke-narrowing constrained Hartmann-Tran profile.•Multi-spectrum line shape analysis and Monte Carlo model indicates strong numerical correlation between Dicke narrowing and speed dependent narrowing mechanisms.•Intensities and broadening coefficients measured with relative uncertainties of 0.15 % and 0.05 %, respectively and line positions measured with 60 kHz uncertainty.•Measurements values of binary absorption coefficients for collision induced absorption spectrum in sub-percent-level agreement with prior work. We present broadband spectroscopic parameters in the a1Δg−X3Σg−(0,0) band of 16O2 centered near 1.27 µm. High-fidelity absorption spectra were acquired on room-temperature air samples over the pressure range of 3.3 kPa to 100 kPa using a length-stabilized cavity ring-down spectrometer, with spectrum frequencies linked to a Cs clock via an optical frequency comb. Parameters were determined by multi-spectrum fitting of advanced line profiles to the measured spectra. This analysis yielded line intensities, positions, collisional broadening and shifting coefficients, Dicke narrowing and speed dependent line shape parameters, first-order line mixing coefficients, and O2-air binary absorption coefficients for collision-induced absorption. We report relative standard uncertainties in the line intensities and broadening coefficients of 0.16 % and 0.05 %, respectively, and line position uncertainties of 60 kHz (2 × 10−6 cm−1). Our analysis reveals strong numerical correlation in fits of the Dicke narrowing and speed dependent widths and shows that inclusion of a recently proposed modification to the Hartmann Tran line profile can increase fitted Dicke narrowing frequencies by as much as 50 %.