Measurements of neutron capture effects on Cd, Sm and Gd in lunar samples with implications for the neutron energy spectrum

Sands, Daphne G.; Laeter, J. R. De; Rosman, K.J.R.

doi:10.1016/s0012-821x(01)00231-x

Cited by 31 publications

(23 citation statements)

References 21 publications

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“…Such neutron capture effects have been observed for lunar soils, which display changes in the 114 Cd/ 113 Cd of up to 5‰ (Sands et al 2001b). Such neutron capture effects have been observed for lunar soils, which display changes in the 114 Cd/ 113 Cd of up to 5‰ (Sands et al 2001b).…”

mentioning

confidence: 68%

Problems and Suggestions Concerning the Notation of Cadmium Stable Isotope Compositions and the Use of Reference Materials

Wombacher

Rehkämper

2004

Geostandard Geoanalytic Res

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Notations for Cd stable isotope compositions and the use of reference materials are discussed. It is proposed that Cd stable isotope data should be reported as variations of the 114Cd/110Cd ratio/ using either the δ114/110Cd or ε114/110Cd notations. Future publications should report results for BAM‐1012 Cd, the only currently available international Cd isotope reference material. It is also recommended that “Münster Cd” and a range of specified geological reference materials are used as additional reference materials. The final choice of a primary “zero‐delta” reference standard remains the most important outstanding question.

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confidence: 68%

Problems and Suggestions Concerning the Notation of Cadmium Stable Isotope Compositions and the Use of Reference Materials

Wombacher

Rehkämper

2004

Geostandard Geoanalytic Res

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“…Isotopes having large neutron-capture cross-sections such as 113 Cd, 149 Sm, 155 Gd and 157 Gd in planetary materials sensitively react with the neutrons produced near the surface of planetary bodies. Therefore, isotopic shifts of 114 Cd/ 113 Cd, 150 Sm/ 149 Sm, 156 Gd/ 155 Gd and 158 Gd/ 157 Gd in extraterrestrial materials have been used to characterize the exposure histories of lunar samples (e.g., Eugster et al, 1970;Russ et al, 1972;Curtis and Wasserburg, 1975;Sands et al, 2001). Up to the present, we have measured the isotopic compositions of Sm and Gd in terrestrial samples Hidaka and Gauthier-Lafaye, 2001), meteorites (Hidaka et al, 1999(Hidaka et al, , 2000a(Hidaka et al, , 2006 and lunar samples (Hidaka et al, 2000b).…”

Section: Introductionmentioning

confidence: 94%

Sm and Gd isotopic shifts of Apollo 16 and 17 drill stem samples and their implications for regolith history

Hidaka

Yoneda

2007

Geochimica et Cosmochimica Acta

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The isotopic compositions of Sm and Gd in lunar regolith samples from the Apollo 16 and 17 deep drill stems showed clear isotopic shifts in 150 Sm / 149 Sm (e = +124 to +191 for A-16, and +37 to +111 for A-17) and 158 Gd/ 157 Gd (e = +107 to +169 for A-16, and +31 to +84 for A-17) corresponding to neutron fluences of (5.68-9.03) · 10 16 n cm À2 for A-16 and (1.85-5.04) · 10 16 n cm À2 for A-17. The depth profiles of neutron fluences suggest that the regoliths at both sites were due to incomplete mixing of three different slabs which experienced individual two-stage irradiation before and after deposition of the upper slabs. The variations in REE compositions provide chemical evidence for incompletely vertical mixing of regoliths especially at upper layers of the two sites. The thermal neutron energy index estimated from the combination of Sm and Gd isotopic shifts, defined as e Sm /e Gd , shows a small variation (0.61-0.64) in the A-16 core except for the surface layer. On the other hand, a large variation in e Sm /e Gd = 0.67 to 0.83 in the A-17 core may result from complicated history such as two-stage irradiation and incomplete mixing during the gardening processes. Isotopic enrichments of 152 Gd and 154 Gd correlated with Eu/Gd elemental abundances and neutron fluences were also observed in almost all of 15 samples, showing evidence of neutron-capture from 151 Eu and 153 Eu, respectively.

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“…, ; Sands et al. ; Hidaka and Yoneda ), aubrites (Hidaka et al. , ), ordinary chondrites (Hidaka et al.…”

Section: Comparison With Previous Modeling and Datamentioning

confidence: 99%

Thermal neutron capture effects in radioactive and stable nuclide systems

Leya

Masarik

2013

Meteorit & Planetary Scien

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Abstract-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 182 Hf-182 W system in iron meteorites, for which neutron capture effects lower the 182 W/ 184 W 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 107 Pd-107 Ag system can be significant and need to be corrected, a result that is in contrast to earlier studies.

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Measurements of neutron capture effects on Cd, Sm and Gd in lunar samples with implications for the neutron energy spectrum

Cited by 31 publications

References 21 publications

Problems and Suggestions Concerning the Notation of Cadmium Stable Isotope Compositions and the Use of Reference Materials

Problems and Suggestions Concerning the Notation of Cadmium Stable Isotope Compositions and the Use of Reference Materials

Sm and Gd isotopic shifts of Apollo 16 and 17 drill stem samples and their implications for regolith history

Thermal neutron capture effects in radioactive and stable nuclide systems

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