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  • 1
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    Nitrogen isotopic fractionations in the low temperature (80 K) vacuum ultraviolet photodissociation of N2 (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-09-16
    Description: N 2 is a diatomic molecule with complex electronic structure. Interstate crossings are prominent in the high energy domain, introducing significant perturbations to the system. Nitrogen mainly photodissociates in the vacuum ultraviolet (VUV) region of the electromagnetic spectrum through both direct and indirect predissociation. Due to the complexity introduced by these perturbations, the nitrogen isotopic fractionation in N 2 photodissociation is extremely hard to calculate, and an experimental approach is required. Here we present new data of N-isotopic fractionation in N 2 photodissociation at low temperature (80 K), which shows a distinctly different 15 N enrichment profile compared to that at relatively higher temperatures (200 and 300 K). The new data, important to understanding the N-isotopic compositions measured in meteorites and other planetary bodies, are discussed in light of the knowledge of N 2 photochemistry and calculated photoabsorption cross sections in the VUV.
    Print ISSN: 0021-9606
    Electronic ISSN: 1089-7690
    Topics: Chemistry and Pharmacology , Physics
    Published by American Institute of Physics (AIP)
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  • 2
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    Sulfur isotopic composition of cenozoic seawater sulfate (1998)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1998-11-20
    Description: A continuous seawater sulfate sulfur isotope curve for the Cenozoic with a resolution of approximately 1 million years was generated using marine barite. The sulfur isotopic composition decreased from 19 to 17 per mil between 65 and 55 million years ago, increased abruptly from 17 to 22 per mil between 55 and 45 million years ago, remained nearly constant from 35 to approximately 2 million years ago, and has decreased by 0.8 per mil during the past 2 million years. A comparison between seawater sulfate and marine carbonate carbon isotope records reveals no clear systematic coupling between the sulfur and carbon cycles over one to several millions of years, indicating that changes in the burial rate of pyrite sulfur and organic carbon did not singularly control the atmospheric oxygen content over short time intervals in the Cenozoic. This finding has implications for the modeling of controls on atmospheric oxygen concentration.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Paytan -- Kastner -- Campbell -- Thiemens -- New York, N.Y. -- Science. 1998 Nov 20;282(5393):1459-62.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉A. Paytan, M. Kastner, and D. Campbell are in the Geosciences Research Division, Scripps Institution of Oceanography, 9500 Gilman Drive, La Jolla, CA 92093, USA. M. H. Thiemens is in the Chemistry Department, University of California, San Dieg.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9822370" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 3
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    Atmospheric science. The mass-independent ozone isotope effect (2001)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2001-07-14
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Thiemens, M H -- New York, N.Y. -- Science. 2001 Jul 13;293(5528):226.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093, USA. mthiemens@ucsd.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11452104" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 4
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    Mass-independent isotope effects in planetary atmospheres and the early solar system (1999)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1999-01-15
    Description: A class of isotope effects that alters isotope ratios on a mass-independent basis provides a tool for studying a wide range of processes in atmospheres of Earth and other planets as well as early processes in the solar nebula. The mechanism for the effect remains uncertain. Mass-independent isotopic compositions have been observed in O3, CO2, N2O, and CO in Earth's atmosphere and in carbonate from a martian meteorite, which suggests a role for mass-independent processes in the atmosphere of Mars. Observed mass-independent meteoritic oxygen and sulfur isotopic compositions may derive from chemical processes in the presolar nebula, and their distributions could provide insight into early solar system evolution.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Thiemens, M H -- New York, N.Y. -- Science. 1999 Jan 15;283(5400):341-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093-0356, USA. mht@chem.ucsd.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9888843" target="_blank"〉PubMed〈/a〉
    Keywords: Atmosphere ; Carbon Dioxide ; *Carbon Isotopes ; Carbon Monoxide ; Extraterrestrial Environment ; Mars ; Meteoroids ; Molecular Weight ; Nitrous Oxide ; *Oxygen Isotopes ; Ozone ; *Planets ; *Solar System
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 5
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    Atmosphere-surface interactions on Mars: delta 17O measurements of carbonate from ALH 84001 (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-06-11
    Description: Oxygen isotope measurements of carbonate from martian meteorite ALH 84001 (delta18O = 18.3 +/- 0.4 per mil, delta17O = 10.3 +/- 0.2 per mil, and Delta17O = 0.8 +/- 0.05 per mil) are fractionated with respect to those of silicate minerals. These measurements support the existence of two oxygen isotope reservoirs (the atmosphere and the silicate planet) on Mars at the time of carbonate growth. The cause of the atmospheric oxygen isotope anomaly may be exchange between CO2 and O(1D) produced by the photodecomposition of ozone. Atmospheric oxygen isotope compositions may be transferred to carbonate minerals by CO2-H2O exchange and mineral growth. A sink of 17O-depleted oxygen, as required by mass balance, may exist in the planetary regolith.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Farquhar, J -- Thiemens, M H -- Jackson, T -- New York, N.Y. -- Science. 1998 Jun 5;280(5369):1580-2.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, University of California San Diego, 92093-0356, USA. jfarquha@ucsd.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9616116" target="_blank"〉PubMed〈/a〉
    Keywords: Atmosphere ; Carbon Dioxide/chemistry ; Carbonates/*chemistry ; Deuterium/chemistry ; Extraterrestrial Environment ; Hot Temperature ; Hydrogen/chemistry ; *Mars ; *Meteoroids ; Oxidation-Reduction ; *Oxygen Isotopes ; Ozone/chemistry ; Photolysis ; Water/chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 6
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    Nylon production: an unknown source of atmospheric nitrous oxide (1991)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1991-02-22
    Description: Nitrous oxide in the earth's atmosphere contributes to catalytic stratospheric ozone destruction and is also a greenhouse gas component. A precise budgetary accounting of N(2)O sources has remained elusive, and there is an apparent lack of source identification. One source of N(2)O is as a by-product in the manufacture of nylon, specifically in the preparation of adipic acid. Characterization of the reaction N(2)O stoichiometry and its isotopic composition with a simulated industrial adipic acid synthesis indicates that because of high rates of global adipic acid production, this N(2)O may account for approximately 10 percent of the increase observed for atmospheric N(2)O.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Thiemens, M H -- Trogler, W C -- New York, N.Y. -- Science. 1991 Feb 22;251(4996):932-4.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17847387" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 7
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    Experimental test of self-shielding in vacuum ultraviolet photodissociation of CO (2008)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2008-09-06
    Description: Self-shielding of carbon monoxide (CO) within the nebular disk has been proposed as the source of isotopically anomalous oxygen in the solar reservoir and the source of meteoritic oxygen isotopic compositions. A series of CO photodissociation experiments at the Advanced Light Source show that vacuum ultraviolet (VUV) photodissociation of CO produces large wavelength-dependent isotopic fractionation. An anomalously enriched atomic oxygen reservoir can thus be generated through CO photodissociation without self-shielding. In the presence of optical self-shielding of VUV light, the fractionation associated with CO dissociation dominates over self-shielding. These results indicate the potential role of photochemistry in early solar system formation and may help in the understanding of oxygen isotopic variations in Genesis solar-wind samples.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Chakraborty, Subrata -- Ahmed, Musahid -- Jackson, Teresa L -- Thiemens, Mark H -- New York, N.Y. -- Science. 2008 Sep 5;321(5894):1328-31. doi: 10.1126/science.1159178.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093-0356, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18772432" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 8
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    Mass-independent oxygen isotopic partitioning during gas-phase SiO2 formation (2013)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2013-10-26
    Description: Meteorites contain a wide range of oxygen isotopic compositions that are interpreted as heterogeneity in solar nebula. The anomalous oxygen isotopic compositions of refractory mineral phases may reflect a chemical fractionation process in the nebula, but there are no experiments to demonstrate this isotope effect during particle formation through gas-phase reactions. We report experimental results of gas-to-particle conversion during oxidation of silicon monoxide that define a mass-independent line (slope one) in oxygen three-isotope space of (18)O/(16)O versus (17)O/(16)O. This mass-independent chemical reaction is a potentially initiating step in nebular meteorite formation, which would be capable of producing silicate reservoirs with anomalous oxygen isotopic compositions.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Chakraborty, Subrata -- Yanchulova, Petia -- Thiemens, Mark H -- New York, N.Y. -- Science. 2013 Oct 25;342(6157):463-6. doi: 10.1126/science.1242237.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093-0356, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24159043" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 9
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    The 18O/16O and 17O/16O ratios in atmospheric nitrous oxide: A mass-independent anomaly (1997)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1997-12-05
    Description: Measurements of the oxygen isotope ratios (18O/16O and 17O/16O) in atmospheric nitrous oxide (N2O) from La Jolla, Pasadena, and the White Mountain Research Station (elevation, 3801 meters) in California and the White Sands Missile Range in New Mexico show that N2O has a mass-independent composition. These data suggest the presence of a previously undefined atmospheric process. The La Jolla samples can be explained by a mixing between an atmospherically derived source of mass-independent N2O and biologically derived mass-dependent N2O. Possible origins of the mass-independent anomaly in N2O are discussed.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Cliff -- Thiemens -- New York, N.Y. -- Science. 1997 Dec 5;278(5344):1774-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, University of California, San Diego, La Jolla, CA 92093-0356, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9388174" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 10
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    Sulfur and hydrogen isotope anomalies in meteorite sulfonic acids (1997)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1997-08-22
    Description: Intramolecular carbon, hydrogen, and sulfur isotope ratios were measured on a homologous series of organic sulfonic acids discovered in the Murchison meteorite. Mass-independent sulfur isotope fractionations were observed along with high deuterium/hydrogen ratios. The deuterium enrichments indicate formation of the hydrocarbon portion of these compounds in a low-temperature environment that is consistent with that of interstellar clouds. Sulfur-33 enrichments observed in methanesulfonic acid could have resulted from gas-phase ultraviolet irradiation of a precursor, carbon disulfide. The source of the sulfonic acid precursors may have been the reactive interstellar molecule carbon monosulfide.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Cooper, G W -- Thiemens, M H -- Jackson, T L -- Chang, S -- New York, N.Y. -- Science. 1997 Aug 22;277(5329):1072-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉SETI Institute and NASA Ames Research Center, MS 239-4, Moffett Field, CA 94035, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9262469" target="_blank"〉PubMed〈/a〉
    Keywords: Alkanesulfonic Acids/*chemistry ; Carbon/chemistry ; *Carbon Compounds, Inorganic ; Deuterium/*analysis ; Hydrogen/*analysis ; Mesylates/chemistry ; *Meteoroids ; Sulfides/chemistry ; *Sulfur Isotopes ; Temperature
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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