Revised rates for the stellar triple-alpha process from measurement of C-12 nuclear resonances
Journal article, 2005
In the centres of stars where the temperature is high enough, three alpha-particles (helium nuclei) are able to combine to form C-12 because of a resonant reaction leading to a nuclear excited state(1). (Stars with masses greater than similar to0.5 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(1), and for determining the size of the iron core of a star just before it goes supernova(2), it has hitherto been insufficiently determined(2). Here we report a measurement of the inverse process, where a C-12 nucleus decays to three alpha-particles. We find a dominant resonance at an energy of similar to11 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-a rate for temperatures from 10(7) K to 10(10) K and find significant deviations from the standard rates(3). Our rate below similar to5 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(4). At temperatures above 10(9) K, our rate is much less, which modifies predicted nucleosynthesis in supernovae(5,6).
PARTICLES
B-12
NUCLEOSYNTHESIS
BETA-DECAY
ELEMENTS
ASTROPHYSICS
STARS
Author
H. O. U. Fynbo
Aarhus University
C. A. Diget
Aarhus University
U. C. Bergmann
CERN
M. J. G. Borge
Spanish National Research Council (CSIC)
J. Cederkall
CERN
P. Dendooven
Kernfysisch Versneller Institut
L. M. Fraile
CERN
S. Franchoo
CERN
V. N. Fedosseev
CERN
B. R. Fulton
University of York
W. X. Huang
University of Jyväskylä
J. Huikari
University of Jyväskylä
H. B. Jeppesen
Aarhus University
A. S. Jokinen
University of Helsinki
University of Jyväskylä
P. Jones
University of Jyväskylä
Björn Jonson
Chalmers, Applied Physics, Subatomic Physics
U. Koster
CERN
K. Langanke
Aarhus University
Mikael Meister
Chalmers
Thomas Nilsson
Chalmers, Applied Physics, Subatomic Physics
Göran Hugo Nyman
Chalmers, Applied Physics, Subatomic Physics
Y. Prezado
Spanish National Research Council (CSIC)
K. Riisager
Aarhus University
S. Rinta-Antila
University of Jyväskylä
O. Tengblad
Spanish National Research Council (CSIC)
M. Turrion
Spanish National Research Council (CSIC)
Y. B. Wang
University of Jyväskylä
L. Weissman
CERN
Katarina Wilhelmsen
Chalmers, Applied Physics, Subatomic Physics
J. Aysto
University of Helsinki
University of Jyväskylä
Nature
0028-0836 (ISSN) 1476-4687 (eISSN)
Vol. 433 7022 136-139Subject Categories (SSIF 2011)
Subatomic Physics
DOI
10.1038/nature03219