title: Sulfur isotopic fractionation in vacuum UV photodissociation of hydrogen sulfide and its potential relevance to meteorite analysis.
abstract: Select meteoritic classes possess mass-independent sulfur isotopic compositions in sulfide and organic phases. Photochemistry in the solar nebula has been attributed as a source of these anomalies. Hydrogen sulfide (H2S) is the most abundant gas-phase species in the solar nebula, and hence, photodissociation of H2S by solar vacuum UV (VUV) photons (especially by Lyman-α radiation) is a relevant process. Because of experimental difficulties associated with accessing VUV radiation, there is a paucity of data and a lack of theoretical basis to test the hypothesis of a photochemical origin of mass-independent sulfur. Here, we present multiisotopic measurements of elemental sulfur produced during the VUV photolysis of H2S. Mass-independent sulfur isotopic compositions are observed. The observed isotopic fractionation patterns are wavelength-dependent. VUV photodissociation of H2S takes place through several predissociative channels, and the measured mass-independent fractionation is most likely a manifestation of these processes. Meteorite sulfur data are discussed in light of the present experiments, and suggestions are made to guide future experiments and models.
authors: Department of Chemistry and Biochemistry, University of California at San Diego, La Jolla, CA 92093-0356.
authors: Subrata
authors: S
authors: Chakraborty
authors: Teresa L
authors: TL
authors: Jackson
authors: Musahid
authors: M
authors: Ahmed
authors: Mark H
authors: MH
authors: Thiemens
mesh_terms: D005591:Chemical Fractionation; D006862:Hydrogen Sulfide / Q000032:analysis*; D019110:Meteoroids; D008956:Models, Chemical; D010777:Photochemistry; D013460:Sulfur Isotopes / Q000032:analysis*; D014466:Ultraviolet Rays; D014618:Vacuum
chemical_list: D013460:Sulfur Isotopes; D006862:Hydrogen Sulfide
keywords: achondrites; chondrites; isotope