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Publication Citation: Absolute Intensities for the O2 1.27 υm Continuum Absorption

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Author(s): B Mate; C Lugez; Gerald T. Fraser; Walter J. Lafferty;
Title: Absolute Intensities for the O2 1.27 υm Continuum Absorption
Published: December 01, 1999
Abstract: Collision-induced absorption coefficients for the 1.27 υm band of O2 have been measured at a resolution of 0.5 cm-1 and an optical pathlength of L = 84 m using a Fourier-transform spectrometer and 2 m long White-type multipass absorption cell. Spectra were recorded for sample densities, ρ, from 1 to 10 times that of an ideal gas under standard conditions (T = 273.15 K and P = 101.325 kPa), i.e., 1 amagat to 10 amagats, at temperatures of 253 K, 273 K, and 296 K, for pure O2 and O2/N2 mixtures. After removing the contributions from the sharp lines of the υ = 0 <- 0 component of the O2 a1δg <- Χ3ςg- band, which overlaps the continuum band, the integrated band strength per unit pathlength, S {identical with} SO2-O2ρO22 + SO2-N2ρN2ρO2, has been determined for several values of the densities, ρO2 and ρN2, to give values for SO2-O2 and SO2-N2. At 296 K we find SO2-O2 = 4.847(22) 10-43 cm-2 (molecule/cm3)-2 [3.499(16) x 10-4 cm-2 amagat-2] and SO2-N2 = 0.941(50) 10-43 cm-2 (molecule/cm3)-2 [0.679(36) x 10-4 cm-2 amagat-2]. Here and elsewhere, Type A expanded uncertainties are given with a coverage factor k = 2. The SO2-O2 coefficient is in reasonable agreement with the previous measurements of Cho et al. [C.W. Cho, E.J. Allin, and H.L. Welsh, Can. J. Phys. 41, 1991-2002 (1963)], however our value of SO2-N2 is a factor of 2.6 times greater than their results. The derived air coefficient, SO2-air, is 37 % greater than the value determined by Mlawer et al. [E.J. Mlawer, S.A. Clough, P.D. Brown, T.M Stephen, J.C. Landry, A. Goldman, and F.J. Murcray, J. Geophys. Res. 103, 3859-3863 (1998)] from an atmospheric measurement, which has been corrected for the most recent value for the absorption coefficients for the overlapping O2 a1{Δ}g <- Χ3Σg- band. The binary collision coefficients are available as a function of frequency for use in atmospheric modeling.
Citation: Journal of Geophysical Research-Atmospheres
Volume: 104
Issue: D23
Keywords: collision-induced absorption;continuum absorption;electronic spectroscopy;forbidden transitions;near infrared intensities;oxygen
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