Absolute Intensities for the O2 1.27 υm Continuum Absorption

Published

December 1, 1999

Author(s)

B Mate, C Lugez, Gerald T. Fraser, Walter J. Lafferty

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 2 a¹δ_g3ς_g^- band, which overlaps the continuum band, the integrated band strength per unit pathlength, S {identical with} S_O2-O2ρ_O2² + S_O2-N2ρ_N2ρ_O2, has been determined for several values of the densities, ρ_O2 and ρ_N2, to give values for S_O2-O2 and S_O2-N2. At 296 K we find S_O2-O2 = 4.847(22) 10^-43 cm^-2 (molecule/cm³)^-2 [3.499(16) x 10^-4 cm^-2 amagat^-2] and S_O2-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 S_O2-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 S_O2-N2 is a factor of 2.6 times greater than their results. The derived air coefficient, S_O2-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}_g3Σ_g^- 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

Pub Type

Journals

Keywords

collision-induced absorption, continuum absorption, electronic spectroscopy, forbidden transitions, near infrared intensities, oxygen

Citation

Mate, B. , Lugez, C. , Fraser, G. and Lafferty, W. (1999), Absolute Intensities for the O₂ 1.27 υm Continuum Absorption, Journal of Geophysical Research-Atmospheres (Accessed November 8, 2024)