Definitions for r-process
r-process

WiktionaryRate this definition:5.0 / 2 votes

1. r-processnoun

   The relatively rapid nucleosynthesis process, in supernovae, in which a large neutron flux allows rapid neutron capture and synthesis of elements up to the transuranic elements.

WikipediaRate this definition:0.0 / 0 votes

1. R-process

   In nuclear astrophysics, the rapid neutron-capture process, also known as the r-process, is a set of nuclear reactions that is responsible for the creation of approximately half of the atomic nuclei heavier than iron, the "heavy elements", with the other half produced by the p-process and s-process. The r-process usually synthesizes the most neutron-rich stable isotopes of each heavy element. The r-process can typically synthesize the heaviest four isotopes of every heavy element, and the two heaviest isotopes, which are referred to as r-only nuclei, can be created via the r-process only. Abundance peaks for the r-process occur near mass numbers A = 82 (elements Se, Br, and Kr), A = 130 (elements Te, I, and Xe) and A = 196 (elements Os, Ir, and Pt). The r-process entails a succession of rapid neutron captures (hence the name) by one or more heavy seed nuclei, typically beginning with nuclei in the abundance peak centered on 56Fe. The captures must be rapid in the sense that the nuclei must not have time to undergo radioactive decay (typically via β− decay) before another neutron arrives to be captured. This sequence can continue up to the limit of stability of the increasingly neutron-rich nuclei (the neutron drip line) to physically retain neutrons as governed by the short range nuclear force. The r-process therefore must occur in locations where there exists a high density of free neutrons. Early studies theorized that 1024 free neutrons per cm3 would be required, for temperatures about 1 GK, in order to match the waiting points, at which no more neutrons can be captured, with the mass numbers of the abundance peaks for r-process nuclei. This amounts to almost a gram of free neutrons in every cubic centimeter, an astonishing number requiring extreme locations. Traditionally this suggested the material ejected from the reexpanded core of a core-collapse supernova, as part of supernova nucleosynthesis, or decompression of neutron-star matter thrown off by a binary neutron star merger in a kilonova. The relative contribution of each of these sources to the astrophysical abundance of r-process elements is a matter of ongoing research.A limited r-process-like series of neutron captures occurs to a minor extent in thermonuclear weapon explosions. These led to the discovery of the elements einsteinium (element 99) and fermium (element 100) in nuclear weapon fallout. The r-process contrasts with the s-process, the other predominant mechanism for the production of heavy elements, which is nucleosynthesis by means of slow captures of neutrons. In general, isotopes involved in the s-process have half-lives long enough to enable their study in laboratory experiments, but this is not typically true for isotopes involved in the r-process. The s-process primarily occurs within ordinary stars, particularly AGB stars, where the neutron flux is sufficient to cause neutron captures to recur every 10–100 years, much too slow for the r-process, which requires 100 captures per second. The s-process is secondary, meaning that it requires pre-existing heavy isotopes as seed nuclei to be converted into other heavy nuclei by a slow sequence of captures of free neutrons. The r-process scenarios create their own seed nuclei, so they might proceed in massive stars that contain no heavy seed nuclei. Taken together, the r- and s-processes account for almost the entire abundance of chemical elements heavier than iron. The historical challenge has been to locate physical settings appropriate for their time scales.

WikidataRate this definition:4.0 / 2 votes

1. r-process

   The r-process is a nucleosynthesis process, that occurs in core-collapse supernovae, and is responsible for the creation of approximately half of the neutron-rich atomic nuclei heavier than iron. The process entails a succession of rapid neutron captures by heavy seed nuclei, typically 56Fe or other more neutron-rich heavy isotopes. The other predominant mechanism for the production of heavy elements is the s-process, which is nucleosynthesis by means of slow captures of neutrons, primarily occurring in AGB stars. The s-process is secondary, meaning that it requires preexisting heavy isotopes as seed nuclei to be converted into other heavy nuclei. Taken together these two processes account for a majority of galactic chemical evolution of elements heavier than iron. The r-process occurs to a slight extent in nuclear weapon explosions.

How to pronounce r-process?

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Numerology

1. Chaldean Numerology

   The numerical value of r-process in Chaldean Numerology is: 6

2. Pythagorean Numerology

   The numerical value of r-process in Pythagorean Numerology is: 5

Examples of r-process in a Sentence

1. Kathleen Behrens:

   The Commissioner (Adam Silver) has acknowledged that we need to do more in this issue in terms of discipline going forward, mostly in terms of due process and not really relying on the criminal justice system.

2. Patricia McCoy:

   Fast forward five years, and two of those banks – Silicon Valley and Signature Bank – failed due to lack of liquidity and possible undercapitalization, their failures destabilized the financial system in the process and caused federal banking regulators to take measures (such as insuring all the deposits at the two failed banks) that will tempt banks to bet on even bigger risks in the future.

3. The Force India boss:

   There were some very important decisions made, quickly and efficiently to deal with issues in Formula One from Austria in terms of penalties. I thought we did a good job with all of that, there are three or four initiatives, if you like, that now need to go through the process.

4. Art Arthur:

   There are so many layers of review and a long vetting process.

5. Oliver Taylor:

   Those Nexcel oil cells, once they're used, come back to Nexcel for recycling where we split them apart, clean and re-use them a number of times. But also we take that used engine oil, we pass it through a re-refining process, and that allows us to use the oil a number of times.

References

1. ^ Wiktionary
   https://en.wiktionary.org/wiki/R-Process
2. ^ Wikipedia
   https://en.wikipedia.org/wiki/R-Process
3. ^ Wikidata
   https://www.wikidata.org/w/index.php?search=r-process