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Author Thrane, Kristine ♦ Connelly, James N. ♦ Bizzarro, Martin ♦ Meyer, Bradley S. ♦ The, Lih-Sin
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword ASTROPHYSICS, COSMOLOGY AND ASTRONOMY ♦ COSMIC RADIATION ♦ CRYSTALLIZATION ♦ HAFNIUM 176 ♦ LUTETIUM 176 ♦ METEORITES ♦ NUCLEAR DECAY ♦ BETA DECAY RADIOISOTOPES ♦ BETA-MINUS DECAY RADIOISOTOPES ♦ DECAY ♦ EVEN-EVEN NUCLEI ♦ HAFNIUM ISOTOPES ♦ HOURS LIVING RADIOISOTOPES ♦ INTERMEDIATE MASS NUCLEI ♦ INTERNAL CONVERSION RADIOISOTOPES ♦ IONIZING RADIATIONS ♦ ISOTOPES ♦ LUTETIUM ISOTOPES ♦ NUCLEI ♦ ODD-ODD NUCLEI ♦ PHASE TRANSFORMATIONS ♦ RADIATIONS ♦ RADIOISOTOPES ♦ RARE EARTH NUCLEI ♦ STABLE ISOTOPES ♦ YEARS LIVING RADIOISOTOPES
Abstract After considerable controversy regarding the {sup 176}Lu decay constant ({lambda}{sup 176}Lu), there is now widespread agreement that (1.867 {+-} 0.008) x 10{sup -11} yr{sup -1} as confirmed by various terrestrial objects and a 4557 Myr meteorite is correct. This leaves the {sup 176}Hf excesses that are correlated with Lu/Hf elemental ratios in meteorites older than {approx}4.56 Ga meteorites unresolved. We attribute {sup 176}Hf excess in older meteorites to an accelerated decay of {sup 176}Lu caused by excitation of the long-lived {sup 176}Lu ground state to a short-lived {sup 176m}Lu isomer. The energy needed to cause this transition is ascribed to a post-crystallization spray of cosmic rays accelerated by nearby supernova(e) that occurred after 4564.5 Ma. The majority of these cosmic rays are estimated to penetrate accreted material down to 10-20 m, whereas a small fraction penetrate as deep as 100-200 m, predicting decreased excesses of {sup 176}Hf with depth of burial at the time of the irradiation event.
ISSN 0004637X
Educational Use Research
Learning Resource Type Article
Publisher Date 2010-07-10
Publisher Place United States
Journal Astrophysical Journal
Volume Number 717
Issue Number 2


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