Thermal neutron capture effects in radioactive and stable nuclide systems

Leya, Ingo; Masarik, Jozef (2013). Thermal neutron capture effects in radioactive and stable nuclide systems. Meteoritics & planetary science, 48(4), pp. 665-685. Meteoritical Society at the University of Arkansas, Dept. of Chemistry and Biochemistry 10.1111/maps.12090

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Neutron capture effects in meteorites and lunar surface samples have been successfully used in the past to study exposure histories and shielding conditions. In recent years, however, it turned out that neutron capture effects produce a nuisance for some of the short-lived radionuclide systems. The most prominent example is the 182Hf-182W system in iron meteorites, for which neutron capture effects lower the 182W/184W ratio, thereby producing too old apparent ages. Here, we present a thorough study of neutron capture effects in iron meteorites, ordinary chondrites, and carbonaceous chondrites, whereas the focus is on iron meteorites. We study in detail the effects responsible for neutron production, neutron transport, and neutron slowing down and find that neutron capture in all studied meteorite types is not, as usually expected, exclusively via thermal neutrons. In contrast, most of the neutron capture in iron meteorites is in the epithermal energy range and there is a significant contribution from epithermal neutron capture even in stony meteorites. Using sophisticated particle spectra and evaluated cross section data files for neutron capture reactions we calculate the neutron capture effects for Sm, Gd, Cd, Pd, Pt, and Os isotopes, which all can serve as neutron-dose proxies, either in stony or in iron meteorites. In addition, we model neutron capture effects in W and Ag isotopes. For W isotopes, the GCR-induced shifts perfectly correlate with Os and Pt isotope shifts, which therefore can be used as neutron-dose proxies and permit a reliable correction. We also found that GCR-induced effects for the 107Pd-107Ag system can be significant and need to be corrected, a result that is in contrast to earlier studies.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences

UniBE Contributor:

Leya, Ingo

Subjects:

500 Science > 520 Astronomy
600 Technology > 620 Engineering
500 Science > 530 Physics

ISSN:

1086-9379

Publisher:

Meteoritical Society at the University of Arkansas, Dept. of Chemistry and Biochemistry

Language:

English

Submitter:

Cléa Serpollier

Date Deposited:

26 Sep 2014 14:59

Last Modified:

06 Jul 2016 15:40

Publisher DOI:

10.1111/maps.12090

Web of Science ID:

000318029400006

BORIS DOI:

10.7892/boris.48841

URI:

https://boris.unibe.ch/id/eprint/48841

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