Unexpectedly large O37ClO/O35ClO intensity ratios of the fluorescence from the low-energy vibrational levels of OClO (Ã 2A2)

Lim, Goo‐Il; Lim, Soon-Mi; Kim, Sang Kyu; Choi, Young Sik

doi:10.1063/1.479325

Cited by 5 publications

(1 citation statement)

References 21 publications

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“…In these three cases, the anomalous isotope effects have been attributed to differences in intersystem crossing (ISC) rates from an initially excited singlet state to a reactive (or dissociative) triplet state. Similar spin-orbit effects have been shown to cause anomalous LIF intensities in 37 ClO 2 vs. 35 ClO 2 for particular vibrational bands (45). A recent study by Muskatel et al (46) demonstrates a theoretical basis for similar isotope effects during the photolysis of N 2 .…”

Section: Results Of Photochemical Experimentsmentioning

confidence: 92%

Vibronic origin of sulfur mass-independent isotope effect in photoexcitation of SO₂and the implications to the early earth’s atmosphere

Whitehill

Xie

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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Signatures of mass-independent isotope fractionation (MIF) † Significant deviations from these mass-dependent scaling laws are referred to as mass-independent fractionation (MIF), and serve as important tracers in the earth and planetary sciences (see refs. 3-5).Early studies suggested that MIF could result only from nucleosynthetic processes (6), and the earliest measurements of oxygen MIF in calcium-aluminum inclusions of meteorites originally were interpreted to be nucleosynthetic in origin (7). It eventually was suggested (8) that chemical processes, such as tunneling or processes associated with predissociation, also might produce MIF. The first experimental evidence for a chemical origin of MIF came from ozone generated by an electric discharge or UV radiation (9, 10). The discovery of oxygen MIF in stratospheric ozone (11) soon triggered intense research into the physiochemical origin of MIF in the ozone system (see refs. 12-14). The possible chemical origins of MIF signatures still are poorly understood.For the sulfur isotope system ( 32 S, 33 S, 34 S, and 36 S), Farquhar et al. (15) made the remarkable discovery that mass-independent sulfur isotope fractionation (S-MIF) is prevalent in sedimentary rocks older than ca. 2.4 Ga but absent in rocks from subsequent periods. The disappearance of S-MIF at about 2.4 Ga (16, 17) signifies a fundamental change in the earth's surface sulfur cycles, and generally is linked to the suppression of both SO 2 photolysis and the formation of elemental sulfur aerosols by the rise of atmospheric oxygen levels (15,18,19). The Archean S-MIF is considered the most compelling evidence for an anoxic early atmosphere and constrains Archean oxygen levels to be less than 10−5 of present levels (19). This model of oxygen evolution, however, depends critically on the assumption that UV photolysis of SO 2 by ∼200 nm radiation is the ultimate source of the anomalous sulfur isotope signature (18). Constraining the source of the S-MIF requires a thorough understanding of the physiochemical origins of S-MIF during the photochemistry of SO 2 .SO 2 exhibits two strong absorption band systems in the UV region: one between 185 nm and 235 nm (C 1 B 2 ←X

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Section: Results Of Photochemical Experimentsmentioning

confidence: 92%

Vibronic origin of sulfur mass-independent isotope effect in photoexcitation of SO₂and the implications to the early earth’s atmosphere

Whitehill

Xie

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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A new class of oxygen isotopic fractionation in photodissociation of carbon dioxide: Potential Implications for atmospheres of Mars and Earth

Bhattacharya

Savarino

Thiemens

2000

Geophysical Research Letters

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The photodissociation and chemistry of CO isotopologues: applications to interstellar clouds and circumstellar disks

Visser

Dishoeck

Black

2009

A&A

541

688

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Aims. Photodissociation by UV light is an important destruction mechanism for carbon monoxide (CO) in many astrophysical environments, ranging from interstellar clouds to protoplanetary disks. The aim of this work is to gain a better understanding of the depth dependence and isotope-selective nature of this process.Methods. We present a photodissociation model based on recent spectroscopic data from the literature, which allows us to compute depth-dependent and isotope-selective photodissociation rates at higher accuracy than in previous work. The model includes self-shielding, mutual shielding and shielding by atomic and molecular hydrogen, and it is the first such model to include the rare isotopologues C 17 O and 13 C 17 O. We couple it to a simple chemical network to analyse CO abundances in diffuse and translucent clouds, photon-dominated regions, and circumstellar disks. Results. The photodissociation rate in the unattenuated interstellar radiation field is 2.6 × 10 −10 s −1 , 30% higher than currently adopted values. Increasing the excitation temperature or the Doppler width can reduce the photodissociation rates and the isotopic selectivity by as much as a factor of three for temperatures above 100 K. The model reproduces column densities observed towards diffuse clouds and PDRs, and it offers an explanation for both the enhanced and the reduced N( 12 CO)/N( 13 CO) ratios seen in diffuse clouds.

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Unexpectedly large O37ClO/O35ClO intensity ratios of the fluorescence from the low-energy vibrational levels of OClO (Ã 2A2)

Cited by 5 publications

References 21 publications

Vibronic origin of sulfur mass-independent isotope effect in photoexcitation of SO₂and the implications to the early earth’s atmosphere

Vibronic origin of sulfur mass-independent isotope effect in photoexcitation of SO₂and the implications to the early earth’s atmosphere

A new class of oxygen isotopic fractionation in photodissociation of carbon dioxide: Potential Implications for atmospheres of Mars and Earth

The photodissociation and chemistry of CO isotopologues: applications to interstellar clouds and circumstellar disks

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Unexpectedly large O37ClO/O35ClO intensity ratios of the fluorescence from the low-energy vibrational levels of OClO (Ã 2A2)

Cited by 5 publications

References 21 publications

Vibronic origin of sulfur mass-independent isotope effect in photoexcitation of SO2and the implications to the early earth’s atmosphere

Vibronic origin of sulfur mass-independent isotope effect in photoexcitation of SO2and the implications to the early earth’s atmosphere

A new class of oxygen isotopic fractionation in photodissociation of carbon dioxide: Potential Implications for atmospheres of Mars and Earth

The photodissociation and chemistry of CO isotopologues: applications to interstellar clouds and circumstellar disks

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Vibronic origin of sulfur mass-independent isotope effect in photoexcitation of SO₂and the implications to the early earth’s atmosphere

Vibronic origin of sulfur mass-independent isotope effect in photoexcitation of SO₂and the implications to the early earth’s atmosphere