s-process


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s-process

A 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.

s-process

[′es ‚prä·səs]
(nuclear physics)
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.
References in periodicals archive ?
He continued with spectroscopy of Magellanic Cloud clusters at Sutherland and confirmed the evolutionary transition from M via S to C stars as due to material being processed by thermonuclear reactions, especially the s-process elements and carbon.
However, the cluster Omega Cen is anomalous and Tom showed the scatter in its colour-magnitude diagram and the presence of strong s-process lines resulted from increasing quantities of processed material from different stellar generations (see e.g.
A spectroscopic study of RV Tauri stars in the Large Magellanic Cloud showed that they have the same range of spectra as their galactic counterparts but that at least one is a carbon star with s-process elements as might be expected if they are post-AGB objects.
Individual papers discuss such matters as nuclear response within a new microscopic multi-phonon approach, information on neutron-rich nuclei from fission X-rays, current experimental developments for s-process nucleosynthesis, fission fragment studies at the mass separator Lohengrin by gamma-ray spectrometry, a gas jet target for radioactive ion beam experiments, and a transition-centric approach to nuclear level scheme determination.
Called the s-process and explained more fully in the article on page 32, it occurs, for example, in intermediate-mass AGB stars at the end of their lives.
These long-lived stars are still around to give evidence about the formation of C, N, O, and s-process elements in their now-departed neighbors.
Accordingly, atoms synthesized via this mechanism are called s-process elements.
Much of the molybdenum and virtually all of the strontium, yttrium, zirconium, barium, lanthanum, cerium, and lead in your body was made by the s-process in the Sun's ancestors and seeded into the cloud from which the Sun and Earth would eventually form.
Heavier elements still, like the lanthanide rare earths, could be reached through slow (s-process) or rapid (r-process) neutron capture, proposed by B2FH and Cameron.
The s-process is very well understood; it indeed occurs in the nuclear-burning regions of low- and intermediate-mass giants nearing the ends of their lives.
The so-called slow-neutron-capture or s-process takes place in red giants.
Unsuspecting students are suddenly asked to remember the difference between Wolf-Rayet and T Tauri stars, X-ray bursters and gamma-ray bursters, the s-process and the r-process, and Type I and Type II supernovae -- not to mention supergranules, superclusters, superconductivity, superfluidity, supersymmetry, supergravity, and superstrings.