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s-processA slow process of nucleosynthesis by which heavy stable nuclei are synthesized from the iron-peak elements (mass number 56) by successive captures of neutrons. The process occurs when there is a low density of neutrons in a star, the neutrons being by-products of nuclear-fusion reactions. If the nucleus produced by a neutron capture is stable it will eventually capture another neutron; if the nucleus is radioactive it will have sufficient time to emit a beta particle (i.e. an electron) to stabilize itself before further neutron capture. Thus the stable isotopes of an element are synthesized until a radioisotope is produced, at which point a new element forms by beta decay. Many years or decades may elapse between successive neutron captures. The most abundant nuclei produced by the s-process will be those with a low ability to capture neutrons. The s-process cannot synthesize nuclei beyond bismuth–209 because neutron capture by this nuclei results in rapid alpha decay. Compare r-process.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006
The synthesis of elements, predominantly in the iron group, over long periods of time through the capture of slow neutrons which are produced mainly by the reactions of α-particles with carbon-13 and neon-21.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.