![]() Many predictions of the local spallation models are testable. The radioactive Be is then entrained by the solar wind and subsequently incorporated into the CAI precursor material. To explain the provenance of 10Be and 7Be in CAIs Bricker and Caffee (2010) propose production of the radionuclides in the solar photosphere by spallation. Its 53-day half-life rules out transport over periods lasting longer than a year or so, and essentially requires a local production model. ![]() (2006) may indicate the presence of 7Be in the early solar system. Finally, measurements by Chaussidon et al. Accordingly, models accounting for the provenance of 10Be in the early solar system involve local mechanisms. Be-10, on the other end cannot be produced nucleosynthetically ( Reeves 1994). Fe-60, in particular, cannot be produced by spallation, and its presence in the solar system indicates the injection of live 60Fe into the solar nebula ( Shukolyukov and Lugmair 1993 Lee et al. On the other hand, if the spallation model holds, prospects improve for probing the energetic particle environment 4.6 Gy ago.Īlthough a single model for the production of all extinct radionuclides in the solar nebula would be satisfying, nuclear physics considerations alone rule out this possibility. Within the spallation model, the isotope ratios shown in Table 1 represent averages over a distribution, possibly broad, of values and their usefulness, for precise dating is lessened or nullified. If production varied with time and/or place, the distribution of extinct radionuclides would have varied, calling into question the idea of a single-valued solar system initial ratio ( Sahijpal and Gupta 2009). Modeling of a closed system with the constraint that 10Be/ 9Be = 0.001 fails to reproduce simultaneously the range of 7Be/ 9Be, 26Al/ 27Al, and 41Ca/Ca ratios inferred for the early solar system from studies of meteorites.Īt the other end of the interpretive spectrum, advocates of local spallation models assume that H + and ionized forms of 3He and 4He accelerated near or on the surface of the early Sun produced the now-extinct radionuclides. For a wide range of parameterizations, the modeled ratios of 7Be/Be and 10Be/Be on the one hand and of 26Al/ 27Al and 41Ca/Ca on the other are coupled because the excitation functions for the relevant nuclear reactions have similar shapes. ![]() For projectiles 1H, 3He, and 4He, we assumed energy spectra of the general form E −α. Our measurements were used to model the production of 7Be, 10Be, 26Al, and 41Ca in the early solar system. Agreement is within 40% for most cross sections. From these results, 26 cross sections were determined and compared with predictions of the TALYS code. The 26Al, 36Cl, and 41Ca were separated chemically, and the numbers of atoms produced in each reaction channel were measured using accelerator mass spectrometry (AMS). The rates of these reactions are important for studies of early solar system irradiation scenarios. Abstract– Cross sections were measured for the nuclear reactions natMg( 3He,x) 26Al, 27Al( 3He,x) 26Al, natCa( 3He,x) 41Ca, and natCa( 3He,x) 36Cl in the energy region from approximately 5–35 MeV.
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