An accurate determination of O2 A-band line intensities through experiment and theory

Abstract

Accurate intensities of the O₂ A-band $[b^1{\Sigma }_g^{+}\leftarrow X^3{\Sigma }_g^{-}(0,0)]$ centered about 760 nm are essential to reduce biases in satellite- and ground-based remote measurements of column-integrated air mass and greenhouse gas concentration. In support of these remote sensing techniques, we made cavity ring-down spectroscopy measurements of ¹⁶O₂ A-band line intensities up to J = 40, and we extrapolated these values to J = 60 using scaled ab initio intensity calculations. The J dependences of the measured and theoretical intensities differ on average by less than 0.1 %, and the measured intensities have relative combined standard uncertainties at the 0.15 % level. Upon evaluation of the integrated intensity, we find a negative bias between literature results and this work, which is four times greater than our present uncertainty.