Astronomy and Astrophysics – Astrophysics
Scientific paper
Aug 1996
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996npfp.conf...21n&link_type=abstract
Nuclear Physics and Fundamental Physics with Neutrons II, p. 21
Astronomy and Astrophysics
Astrophysics
Nuclear Astrophysics, Neutrons, Capture Effect, Neutron Physics, Big Bang Cosmology, Absorption Cross Sections, Abundance, Stellar Composition, Heavy Elements, Stellar Temperature, Neutron Sources, Carbon 13, Neon Isotopes, Oxygen Isotopes, Metallicity
Scientific paper
Models of the stellar evolution and nucleosynthesis in stars is necessary to investigate the record of the Big Bang. The observed abundances of various elements in stars could be used to construct the models. Since the heavier elements than iron are considered to be synthesized by the neutron capture reaction of a nucleus in stars, it is necessary to measure the reaction cross section at stellar temperature to estimate quantitatively the production yield of these elements. To this purpose pulsed keV neutrons from the JBP spallation source would be very useful. In order to reveal the record of the Big Bang it is necessary to construct the models of the chemical evolution of the Galaxy, which could be made by constructing the models of it's composition. Therefore, it is quite important to construct the models of the stellar evolution and nucleosynthesis. The observed abundances of various elements in stars have been playing an important role to construct the models of the stellar evolution. Those elements heavier than iron are considered to be synthesized by the two neutron capture reactions of rapid-(r) and slow-(s) processes in stars at stellar temperature of around 108 K, which corresponds to the neutron kinetic energy between 10 and 300 keV. Here, although the astrophysical site of the r-process remains as an open problem to be solved, that of the s-process is claimed to be the He-burning shell of an asymptotic giant branch star. The neutrons from the C-13(alpha,n)O-16 and Ne-22(alpha,n)Mg-25 reactions are considered as the neutron source for the s-process isotopes, and pre-existing Fe (seed nucleus) reacts with these neutrons, producing the heavier elements. Therefore, it is necessary to measure the neutron capture cross sections of various nuclei at stellar temperature to know the production yields of s-process isotopes. One of our recent works on the neutron capture reaction of a nucleus is discussed.
Baba Takayasu
Igashira Masayuki
Kii Tsuneo
Kikuchi Tatsuru
Kobayashi Tatsuo
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