Pub Date : 2017-01-01Epub Date: 2016-08-10DOI: 10.7566/JPSCP.14.011005
Olga Pravdivtseva, Alex Meshik, Charles M Hohenberg
The preserved record of decay of now-extinct 129I into 129Xe forms the basis of the I-Xe chronometer. Comparison of the high precision I-Xe and Pb-Pb ages of chondrules and pure mineral phases separated from eight meteorites suggests the 17.5 ÷ 14.6 Ma range for the 129I half-life, assuming that the 235U and 238U half-lives are correct. The mean value of 16 Ma indicates that the 15.7 Ma half-life of 129I used here for the I-Xe age calculations is most probably correct. Since the 129I half-life value only affects the relative I-Xe ages, the few Ma relative to the Shallowater standard, the absolute I-Xe ages are almost immune to this uncertainty in the 129I half-life.
{"title":"Evaluation of the <sup>129</sup>I Half-Life Value Through Analyses of Primitive Meteorites.","authors":"Olga Pravdivtseva, Alex Meshik, Charles M Hohenberg","doi":"10.7566/JPSCP.14.011005","DOIUrl":"https://doi.org/10.7566/JPSCP.14.011005","url":null,"abstract":"<p><p>The preserved record of decay of now-extinct <sup>129</sup>I into <sup>129</sup>Xe forms the basis of the I-Xe chronometer. Comparison of the high precision I-Xe and Pb-Pb ages of chondrules and pure mineral phases separated from eight meteorites suggests the 17.5 ÷ 14.6 Ma range for the <sup>129</sup>I half-life, assuming that the <sup>235</sup>U and <sup>238</sup>U half-lives are correct. The mean value of 16 Ma indicates that the 15.7 Ma half-life of <sup>129</sup>I used here for the I-Xe age calculations is most probably correct. Since the <sup>129</sup>I half-life value only affects the relative I-Xe ages, the few Ma relative to the Shallowater standard, the absolute I-Xe ages are almost immune to this uncertainty in the <sup>129</sup>I half-life.</p>","PeriodicalId":92090,"journal":{"name":"JPS conference proceedings","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.7566/JPSCP.14.011005","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"35565380","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-01-01Epub Date: 2016-09-17DOI: 10.7566/JPSCP.14.010303
Sachiko Amari
Presolar SiC and graphite grains are the grain types whose isotopic signatures have been extensively studied. Isotopic compositions of light and intermediate elements in single grains have been analyzed mostly using secondary ion mass spectrometry. Detailed information about nucleosynthetic conditions can be obtained from isotopic compositions of heavy elements. Isotopic compositions of heavy elements in SiC and graphite grains have been analyzed using resonant ionization mass spectrometry. Analyses of heavy elements and noble gases are likely to produce new insights into presolar grains using newly-developed instruments.
{"title":"Nucleosynthetic Signatures in Presolar SiC and Graphite Grains.","authors":"Sachiko Amari","doi":"10.7566/JPSCP.14.010303","DOIUrl":"10.7566/JPSCP.14.010303","url":null,"abstract":"<p><p>Presolar SiC and graphite grains are the grain types whose isotopic signatures have been extensively studied. Isotopic compositions of light and intermediate elements in single grains have been analyzed mostly using secondary ion mass spectrometry. Detailed information about nucleosynthetic conditions can be obtained from isotopic compositions of heavy elements. Isotopic compositions of heavy elements in SiC and graphite grains have been analyzed using resonant ionization mass spectrometry. Analyses of heavy elements and noble gases are likely to produce new insights into presolar grains using newly-developed instruments.</p>","PeriodicalId":92090,"journal":{"name":"JPS conference proceedings","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6364310/pdf/nihms-1005142.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"36947300","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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