S-process BA isotopic compositions in presolar SiC from the Murchison meteorite

Prombo, C. A.; Podosek, F. A.; Amari, S.; Lewis, R. S.

doi:10.1086/172756

Cited by 85 publications

(83 citation statements)

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“…Quite similar isotope variations for noble gases are observed in presolar diamonds (Verchovsky et al 1998) and SiC (Lewis et al 1994) grain-size fractions, as well as for Ba (Zinner, Amari & Lewis 1991;Prombo, Podosek, Amari et al 1993) and Sr (Prombo, Podosek, Amari et al 1992) in SiC grains. Thus, through measurements of the grain size and isotopic compositions of samples representing a collection of grains irradiated in space, it is possible to identify different implanted components provided their implantation energies are not identical, and also to calculate the implantation energies.…”

Section: Isotope Effectssupporting

confidence: 53%

Ion Implantation into Presolar Grains: A Theoretical Model

Verchovsky

Wright

Pillinger

2003

Publ. – Astron. Soc. Aust

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A numerical model for ion implantation into spherical grains in free space has been developed. It can be applied to single grains or collections of grains with known grain-size distributions. Ion-scattering effects were taken into account using results of computer simulations. Possible isotope and element fractionation of the implanted species was investigated using this model. The astrophysical significance of the model lies in the possible identification of energetically different components (such as noble gases) implanted into presolar grains (such as diamond and SiC) and in establishing implantation energies of the components.

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Section: Isotope Effectssupporting

confidence: 53%

Ion Implantation into Presolar Grains: A Theoretical Model

Verchovsky

Wright

Pillinger

2003

Publ. – Astron. Soc. Aust

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“…A seeond problem, which requires aeeurate cross sections, is related to the !arge isotopic anomalies in barium, whieh were reeently diseovered in SiC grains, a very resistant fraction of earbonaeeous ehondrite meteorites [7][8] [9]. If these anomalies are interpreted as being clue to an admixture of pure s-process barium to the ordinary solar system abundances, the expectecl yields, N s, have to be known reliably.…”

Section: Introductionmentioning

confidence: 99%

Stellar neutron capture cross sections of the Ba isotopes

et al. 1994

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The neutron capture cross sections of 134 Ba, 135 Ba, 136 Ba, and 137 Ba were measured in the energy range from 5 to 225 keV at the Karlsruhe 3.75 MV Van de Graaff accelerator. Neutrons were produced via the 7 Li(p,nfBe reaction by bombarding metallic Li targets with a pulsed proton beam. Capture events were registered with the Karlsruhe 47r Barium Fluoride Detector. Several runs have been performed under different experimental conditions to study the systematic uncertainties, which resulted mainly from the large ratios of total to capture cross sections of up to 400. The cross section ratios were determined with an overall uncertainty of "'3%, an improvement by factors of five to eight compared to existing data. Severe discrepancies were found with respect to previous results. Maxwellian averaged neutron capture cross sections were calculated for thermal energies between kT = 10 ke V and 100 ke V. These stellar cross sections were used in an s-process analysis. For the s-only isotopes 134 Ba and 136 Ba the Nsratio was determined to 0.875±0.025. Hence, a significant brauehing of the s-process path at 134 Cs can be claimed for the first time, in cantrast to predictions from the classical approach. This brauehing yields information on the s-process temperature, indicating values araund T 8 = 2. The new cross sections arealso important for the interpretation of barium isotopic anomalies, which were recently discovered in SiC grains of carbonaceous chondrite meteorites. Tagether with the results from previous experiments on tellurium and samarium, a general improvement of the Nssystematics in the mass range A = 120 to 150 is achieved. This allows for a more reliable separation of s-and r-process yields, resulting in an improved assignment of the respective contributions to eiemental barium that is required for comparison with stellar observations. ZUSAMMENFASSUNG

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“…Silicon isotopic ratios in mainstream, Y and Z grains show a systematic trend. First, average 29 Si/ 28 Si ratios systematically decrease from mainstream Bulk analyses of SiC-rich fractions show that they are enriched in s-process Kr [26][27][28], Xe [27,28], Sr [29], Ba [30][31][32], Nd and Sm [31]. Since the majority of SiC grains are mainstream grains, the s-process enrichments were most likely carried by mainstream grains.…”

Section: Silicon Carbidementioning

confidence: 99%

Nucleosynthetic Signatures in Presolar SiC and Graphite Grains

Amari¹

2017

Proceedings of the 14th International Symposium on Nuclei in the Cosmos (NIC2016)

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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.

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S-process BA isotopic compositions in presolar SiC from the Murchison meteorite

Cited by 85 publications

References 0 publications

Ion Implantation into Presolar Grains: A Theoretical Model

Ion Implantation into Presolar Grains: A Theoretical Model

Stellar neutron capture cross sections of the Ba isotopes

Nucleosynthetic Signatures in Presolar SiC and Graphite Grains

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