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Closed Access item Revised rates for the stellar triple-alpha process from measurement of C-12 nuclear resonances

Authors:Fynbo, H. O. U.
Diget, C. Aa.
Bergmann, U. C.
García Borge, María José
Cederkäll, Joakim
Dendooven, Peter
Fraile, Luis M.
Franchoo, Serge
Fedosseev, Valentin N.
Fulton, Brian R.
Huang, Wenxue
Huikari, Jussi
Jeppesen, Henrik B.
Jokinen, Ari S.
Jones, Peter
Jonson, Björn
Köster, Ulli
Langanke, Karlheinz
Meister, Mikael
Nilsson, Thomas
Nyman, Göran
Prezado, Yolanda
Riisager, Karsten
Rinta-Antila, Sami
Tengblad, Olof
Turrión, Manuela
Wang, Youbao
Weissman, Leonid
Wilhelmsen, Katarina
Äystö, Juha
Issue Date:13-Jan-2005
Publisher:Nature Publishing Group
Citation:Nature 433(7022): 136-139 (2005)
Abstract:In the centres of stars where the temperature is high enough, three α-particles (helium nuclei) are able to combine to form C-12 because of a resonant reaction leading to a nuclear excited state. (Stars with masses greater than ~ 0.5 times that of the Sun will at some point in their lives have a central temperature high enough for this reaction to proceed). Although the reaction rate is of critical significance for determining elemental abundances in the Universe, and for determining the size of the iron core of a star just before it goes supernova, it has hitherto been insufficiently determined. Here we report a measurement of the inverse process, where a C-12 nucleus decays to three α-particles. We find a dominant resonance at an energy of ~ 11 MeV, but do not confirm the presence of a resonance at 9.1 MeV (ref. 3). We show that interference between two resonances has important effects on our measured spectrum. Using these data, we calculate the triple-α rate for temperatures from 10^7 K to 10^10 K and find significant deviations from the standard rates. Our rate below ~ 5 x 10^7 K is higher than the previous standard, implying that the critical amounts of carbon that catalysed hydrogen burning in the first stars are produced twice as fast as previously believed. At temperatures above 10^9 K, our rate is much less, which modifies predicted nucleosynthesis in supernovae.
Description:4 pages, 3 figures.-- PMID: 15650733 [PubMed].
Publisher version (URL):http://dx.doi.org/10.1038/nature03219
ISSN:0028-0836 (Print)
Appears in Collections:(CFMAC-IEM) Artículos

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