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 Title: A SPECTROSCOPIC PERTURBATION ORIGIN FOR SULFUR MASS INDEPENDENT FRACTIONATION VIA THE B-X SYSTEM OF S2 Author(s): Hull, Alexander W. Contributor(s): Field, Robert W.; Ono, Shuhei Subject(s): Atmospheric science Abstract: The Great Oxygenation Event (GOE), the introduction of O$_{2}$ into the Earth’s atmosphere approximately 2.4 billion years ago, is a critical signpost in the development of life on Earth. The vanishing of sulfur isotope anomalies, called Sulfur Mass-Independent Fractionation (S-MIF), in the rock record is thought to be correlated with oxygenation of the early atmosphere. However, the mechanism for the generation of S-MIF in an anoxic atmosphere is unknown. Here, I propose a mechanism that involves spectroscopic perturbations in the B-X UV band system of S$_{2}$. This proposal is based on a global deperturbation analysis done by Green and Western\footnote{M.E. Green, C.M. Western, A deperturbation analysis of the B $^{3}$$\Sigma$$_{u}$$^- (v' = 0-6) and the B" ^{3}$$\Pi$$_{u} (v' = 2-12) states of S_{2}, J. Chem. Phys. 104 (3) (1996) 848-864.} \footnote{M.E. Green, C.M. Western, Upper vibrational states of the B" ^{3}$$\Pi$$_{u}$ state of $^{32}$S$_{2}$, J. Chem. Soc., Faraday Trans. 93 (3) (1997) 365-372.} and work that I presented previously at this conference in 2015 (MG12) and 2016 (MG08). Specifically, perturbations of the “bright” B state by a “dark” B” state cause some isotopologues to have longer average excited state lifetimes than others. I demonstrate a difference between the shorter-lifetime symmetric (e.g. $^{32}$S-$^{32}$S) isotopologues of S2, for which nuclear permutation symmetry causes half of the rotational lines to be missing, and the longer-lifetime asymmetric isotopologues (e.g. $^{33}$S-$^{32}$S). I also comment on general features of the B/B” system of S$_{2}$ that make it uniquely well-suited to generate a large MIF isotope effect. Issue Date: 06/22/18 Publisher: International Symposium on Molecular Spectroscopy Citation Info: APS Genre: Conference Paper / Presentation Type: Text Language: English URI: http://hdl.handle.net/2142/100717 DOI: 10.15278/isms.2018.FF03 Other Identifier(s): FF03 Date Available in IDEALS: 2018-08-172018-12-12
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