The 1.27 m O2 Continuum Absorption in O2/CO2 Mixtures

Published

December 1, 2001

Author(s)

Gerald T. Fraser, Walter J. Lafferty

Abstract

The collision-induced, near-infrared O₂ continuum band overlapping the weak α¹δg - X³ς-_g, v=O -0, 1.27 m discrete band of O₂ has been investigated in O₂/CO₂ mixtures at room temperature (T=296 K) for total densities from 1.8 to 9.3 times that of an ideal gas under standard conditions (T=273.15 K and P =101.325 kPa), i.e., from 1.8 to 9.3 amagats. Absorption spectra were recorded at 0.5 cm^-1 resolution using a Fourier-transform spectrometer and an 84-m optical pathlength through the gas sample. A least-squares analysis of the integrated band strength, ^Stotal = ^SO₂ PO₂ =SO₂-O₂ PO₂²+SO₂-CO₂PO₂PCO₂, as a function of carbon dioxide density, PCO₂, and oxygen density, PO₂, yields SO₂-CO₂ = 2.95(40) x 10^-43 cm^-2(molecule/cm³)-2 [i.e., 2.13(29) x 10⁰⁴ cm^-2 amagat^-2]. The SO₂-CO₂ coefficient is approximately three times greater than the corresponding SO₂-N₂ coefficient determined from studies of O₂/N₂ mixtures, illustrating the efficiency of large electric multipolar moments in inducing continuum absorption in the 1.27 m band of O₂. Furthermore, the results suggest the potential importance of water, with its large electric dipole moment, in enhancing the collision-induced absorption bands of O₂ and N₂ in the atmosphere. Indeed, the apparent inability of radiative-transfer models to accurately account for the increased atmospheric absorption present when water-vapor levels increase may be due in part to the neglect of the intensity enhancement of a number of continuum bands and the far wings of discrete bands by water collisions.

Citation

Journal of Geophysical Research-Atmospheres

Volume

106

Issue

No. D23

Pub Type

Journals

Keywords

atmospheric absorption, carbon dioxide, CIA, collision-induced absorption, continuum absorption, molecular oxygen, near infrared

Citation

Fraser, G. and Lafferty, W. (2001), The 1.27 m O₂ Continuum Absorption in O₂/CO₂ Mixtures, Journal of Geophysical Research-Atmospheres (Accessed October 10, 2025)