Revised rates for the stellar triple-alpha process from measurement of C-12 nuclear resonances
Artikel i vetenskaplig tidskrift, 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

BETA-DECAY

NUCLEOSYNTHESIS

ELEMENTS

ASTROPHYSICS

STARS

Författare

H. O. U. Fynbo

Aarhus Universitet

C. A. Diget

Aarhus Universitet

U. C. Bergmann

European Organization for Nuclear Research

M. J. G. Borge

CSIC - Instituto de Estructura de la Materia (IEM)

J. Cederkall

European Organization for Nuclear Research

P. Dendooven

Kernfysisch Versneller Institut

L. M. Fraile

European Organization for Nuclear Research

S. Franchoo

European Organization for Nuclear Research

V. N. Fedosseev

European Organization for Nuclear Research

B. R. Fulton

University of York

W. X. Huang

Jyväskylän Yliopisto

J. Huikari

Jyväskylän Yliopisto

H. B. Jeppesen

Aarhus Universitet

A. S. Jokinen

Helsingin Yliopisto

Jyväskylän Yliopisto

P. Jones

Jyväskylän Yliopisto

Björn Jonson

Chalmers, Teknisk fysik, Subatomär fysik

U. Koster

European Organization for Nuclear Research

K. Langanke

Aarhus Universitet

Mikael Meister

Chalmers

Thomas Nilsson

Chalmers, Teknisk fysik, Subatomär fysik

Göran Hugo Nyman

Chalmers, Teknisk fysik, Subatomär fysik

Y. Prezado

CSIC - Instituto de Estructura de la Materia (IEM)

K. Riisager

Aarhus Universitet

S. Rinta-Antila

Jyväskylän Yliopisto

O. Tengblad

CSIC - Instituto de Estructura de la Materia (IEM)

M. Turrion

CSIC - Instituto de Estructura de la Materia (IEM)

Y. B. Wang

Jyväskylän Yliopisto

L. Weissman

European Organization for Nuclear Research

Katarina Wilhelmsen

Chalmers, Teknisk fysik, Subatomär fysik

J. Aysto

Jyväskylän Yliopisto

Helsingin Yliopisto

Nature

0028-0836 (ISSN) 1476-4687 (eISSN)

Vol. 433 7022 136-139

Ämneskategorier

Subatomär fysik

DOI

10.1038/nature03219