15min:

C. L. LUGEZ, A. M. SOLODOV, W. J. LAFFERTY AND G. T. FRASER, OPTICAL TECHNOLOGY DIVISION, NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY, GAITHERSBURG, MD 20899.

Measurements of the collision-induced absorption of O₂ in the vicinity of the electric-dipole-forbidden vibrational fundamental have been made in pure O₂, O₂/N₂ and Ar/O₂ mixtures. The goal is to provide reliable absorption coefficients to allow accurate retrievals of stratospheric concentration profiles of H₂O vapor, NO₂, and sulfate aerosols from limb-viewing filter radiometers, such as those mounted on the UARS and future EOS platforms. Here, spectra were recorded at a resolution of 0.5 cm^-1 using a Fourier-transform infrared spectrometer. Measurements were made using an optical pathlength of 84 m, sample densities up to approximately 8 amagats, and sample temperatures between 225 K and 300 K. The present results are in good agreement with the earlier less precise measurements of Orlando et al. on O₂ and O₂/N₂ mixtures and Thibault et al. on pure O₂. Studies of Ar/O₂ mixtures indicate that the observed structure on the high-frequency shoulder of the band, previously attributed to dimer bound states by Henderson and Ewing, is more likely due to line mixing of pure quadrupole transitions of O₂, as originally suggested by Vigasin.