# $O_{2}$ PHOTOABSORPTION IN THE $40950-41300 CM^{-1}$ REGION: NEW HERZBERG BANDS, NEW ABSORPTION LINES, AND IMPROVED SPECTROSCOPIC DATA

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 Title: $O_{2}$ PHOTOABSORPTION IN THE $40950-41300 CM^{-1}$ REGION: NEW HERZBERG BANDS, NEW ABSORPTION LINES, AND IMPROVED SPECTROSCOPIC DATA Creators: Slanger, T. G.; Huestis, D. L.; Cosby, P. C.; Naus, Hans; Meijer, Gerard Issue Date: 1996 Publisher: Ohio State University Abstract: The technique of cavity ring-down (CRD) spectroscopy is particularly useful for measuring absorptions of very weak optical transitions. We have in this manner investigated the $40950-41300 cm^{-1}$ region in $O_{2}$, where only absorption in the $O_{2}(A^{3}\Sigma^{+}_{u}- X^{3}\Sigma^{-}_{g}$) 11-0 band had been previously identified. Five new bands have been discovered in this range - the ($A^{3}\Delta_{u} - X^{3}\Sigma^{-}_{g}$) 12-0 and 13-0 bands, the $c^{1}\Sigma_{u}^{-} - X^{3}\Sigma^{-}_{g}$ 17-0 and 18.0 bands, and the $A^{3}\Sigma^{+}_{u}- X^{3}\Sigma^{-}_{g}$ 12-0 band. The origins of the $F_{1}$ and $F_{2}$ components of the latter lie only $7 cm^{-1}$ below the lowest dissociation limit, and 14 lines have been identified. No $F_{3}$ levels were observed; apparently all are above the dissociation limit. The high instrumental sensitivity of the CRD technique has allowed observation of weak lines of the A-X 11-0 band, and 12 of the 13 branches have been identified and their intensities measured. A very low upper limit has been set on the intensity of the thirteenth branch $Q_{13}$. We find 106 unidentified lines in the region, the stronger ones (18) lying in the vicinity of lines of the A-X 11-0 band. The weaker ones (88) are spread throughout the spectral region, up to and even beyond the $O_{2}$ dissociation limit, and probably have their origin in transitions to very weakly bound $O_{2}$ states, which may have atmospheric significance. These weaker lines have intensities that are typically 1-5% of the strong A-X 11-0 band lines. Description: Author Institution: Molecular Physics Laboratory, SRI International; Dept. of Molecular and Laser Physics, University of Nijmegen URI: http://hdl.handle.net/1811/13540 Other Identifiers: 1996-RE-07