Integrated absorption intensity and Einstein coefficients for the O2 a 1Δg–X 3Σg− (0,0) transition: A comparison of cavity ringdown and high resolution Fourier transform spectroscopy with a long-path absorption cell

Abstract

The two experimental techniques of cavity ringdown spectroscopy and high-resolution, long-path Fourier transform spectroscopy have been used to measure quantitative absorption spectra and determine the integrated absorption intensity (Sint,B) for the O2 a 1Δg–X 3Σg− (0,0) band. Einstein A-factors and radiative lifetimes for the O2 a 1Δg v=0 state have been derived from the Sint,B values. The two methods give values for the integrated absorption intensity that agree to within 2%. The value recommended from the results of this study is Sint,B=3.10±0.10×10−24 cm molecule−1, corresponding to an Einstein-A coefficient of A=2.19±0.07×10−4 s−1 and a radiative lifetime of τrad=76 min. The measurements are in excellent agreement with the recent absorption study of Lafferty et al. [Appl. Opt. 37, 2264 (1998)] and greatly reduce the uncertainty in these parameters, for which accurate values are required for determination of upper stratospheric and mesospheric ozone concentrations.