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.
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.
The s-process was thought to occur in the cores of highly evolved red giants, following the discovery of the unstable element technetium in the spectra of a few such objects.
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.