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Total Pressure Dependence of Sulfur Mass‐Independent Fractionation by SO 2 Photolysis
Author(s) -
Endo Yoshiaki,
Danielache Sebastian O.,
Ueno Yuichiro
Publication year - 2019
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2018gl080730
Subject(s) - total pressure , mass independent fractionation , atmosphere (unit) , isotopologue , fractionation , analytical chemistry (journal) , chemistry , photodissociation , sulfur , absorption (acoustics) , materials science , environmental chemistry , thermodynamics , physics , isotope fractionation , chromatography , organic chemistry , molecule , composite material
Sulfur Mass‐Independent Fractionation (S‐MIF) may provide a clue to understanding Earth's early atmosphere. We examined total pressure dependence of the S‐MIF produced by SO 2 photolysis. Isotopic self‐shielding is known to produce S‐MIF, which could be changed by both the partial pressure of SO 2 ( p SO 2 ) and by the total pressure ( p Total). Our experimental results show that both Δ 33 S and Δ 36 S values are constant when total pressure is below 10 kPa at constant p SO 2 , whereas they decrease as total pressure increases. The result suggests that pressure broadening of the SO 2 absorption line is responsible for the S‐MIF. The modeled high‐resolution isotopologue cross sections can reproduce our experimental results and its changes depending on both p SO 2 and p Total. Consequently, we conclude that the Archean Δ 33 S and Δ 36 S correlation can only be achieved when the total pressure of the Archean atmosphere was below 100 kPa, or it was produced in the upper atmosphere.