Accurate Laboratory Measurement of Collision-Induced Absorption of O2 near 1.06 µm

The O₂ collision-induced absorption(CIA) band near 1.06 μm plays a crucial role in evaluating planetary habitability. This band consists of the    transition superimposed on a broad CIA structure. Although the O₂ CIA in this band is much weaker than that near 1.27 μm and the A band (760 nm), accurate binary coefficients, , were measured using a custom designed, high-sensitivity cavity ring-down spectroscopy (CRDS) setup developed in our laboratory under low density (< 1 amagat) and at room temperature (296 K) for pure O₂ and O₂/N₂ mixtures over the range 9120-9820 cm^-1. As expected, excellent agreement, generally within 1%, was observed among measurements performed at different densities, benefiting from the use of Ar as a baseline reference and low-density measurements that suppress Rayleigh scattering and line mixing, thereby reducing the uncertainty of the retrieved results. The retrieved  were compared with the values from LBLRTM simulations, HITRAN, and ab initio calculations. The  reported here are found to be in good agreement with these values. In particular, excellent agreement within 0.2% is observed between our measurements and LBLRTM simulations at the band center. The integrated CIA band intensity, , exceeds the corresponding values in HITRAN, LBLRTM simulations, and the ab initio calculations by about 28.6%, 44.2%, and 16.5%, respectively.