R-process

The r-process (r for english rapid, fast ') is one of the Nukleosyntheseprozesse.

It is a Neutroneneinfangprozess that occurs at high neutron densities and temperatures, in contrast to the slow S- process. In this unstable neutron-rich nuclei are built up by a high neutron flux, which decompose rapidly to stable neutron-rich nuclei of heavy elements from iron to lead as well as the unstable long-lived isotopes of bismuth, thorium, uranium and plutonium.

The location of the R- process is not known with certainty. Currently, two processes are mainly discussed: first, the merger of two neutron stars (kilo Nova ) and on the other supernova explosions. Is considered most likely that the r- process occurs during supernovae at the end of the life cycle of a star. This neutron- rich material is determined by the shock wave that originated at the incompressible degenerate neutron core ( see neutron star ) takes in the center of the star, swept away by the outer area and hurled into space.

The relatively low frequency of synthesized in the r- process elements presupposes, however, that either only a small fraction of supernovae it is emitting to space, or that any supernova emits only a small amount of it.

Due to the very high neutron flux (on the order of more than 10 billion billion = 1022 neutrons per square centimeter per second) very many neutrons deposits can in a split second to take place, especially on unstable intermediates before even a radioactive β - decay occurs. The process is slowed down only by three factors:

At each Neutronenanlagerung energy is in the form of a gamma quantum γ free, increase mass number A and neutron number N is generated by 1 and a new isotope.

In the subsequent β - decay of unstable isotopes, a neutron is converted by each emitting an electron e and an electron anti-neutrinos in a proton. This creates an atom of another element with the same mass number, but increased by 1 atomic number Z ( number of protons ) and decreased by 1 neutron number N; the atom moves in the periodic table.

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