Rp-process

Information about Rp-process

The rp-process (rapid proton capture process) consists of consecutive proton captures onto seed nuclei to produce heavier elements[1]. It is a nucleosynthesis process and, along with the s process and the r process, may be responsible for the generation of many of the heavy elements present in the universe. However, it is notably different from the other processes mentioned in that it occurs on the proton-rich side of stability as opposed to on the neutron-rich side of stability. The end point of the rp-process (the highest mass element it can create) is not yet well established, but recent research has indicated that in neutron stars it cannot progress beyond tellurium.[2] The rp-process is inhibited by alpha decay, which puts an upper limit on the end point at 105Te, the lightest observed alpha decaying nuclei[3], though lighter isotopes of tellurium are also believed to be stable and alpha decaying.

Conditions

The process has to occur in very high temperature environments (above 1 x 109 kelvins or 1 gigakelvin) so that the protons can overcome the large coulomb barrier for charged particle reactions. A hydrogen rich environment is also a prerequisite due to the large proton flux needed. The seed nuclei needed for this process to occur are thought to be formed during breakout reactions from the hot CNO cycle. Typically proton capture in the rp-process will compete with (α,p) reactions, as most environments with a high flux of hydrogen are also rich in helium. The time-scale for the rp-process is set by β+ decays at or near the proton drip line, because the weak interaction is notoriously slower than the strong interaction and electromagnetic force.

Possible sites

Sites suggested for the rp-process are binary systems where one star is a compact object, either low mass black hole or neutron star. In these systems a star (often a red giant) is feeding material onto its compact partner star. The accreted material is rich in hydrogen and helium because of its origin from the surface layers of the accreting star. Because compact stars have high gravitational fields, the material falls with a high velocity towards the compact star, usually colliding with other accreted material en route, forming an accretion disk. In the case accretion onto a neutron star, as this material slowly builds up on the surface, it will have a high temperature, typically around 1 x 108 K, and it is thus electron degenerate. Eventually, it is believed that thermal instabilities arise in this hot atmosphere, and because of the electron degeneracy of the matter, increases in temperature do not lead to a notable increase in pressure, and so the temperature will continue to rise until it leads to a runaway thermonuclear explosion, which we call the rp-process in this case. Observationally, the rp-process in neutron star binaries is seen as an X-ray burst.

References

1. ^ Lars Bildsten, "Thermonuclear Burning on Rapidly Accreting Neutron Stars" in The Many Faces of Neutron Stars, ed. R. Buccheri, J. van Paradijs, & M. A. Alpar (Kluwer), 419 (1998)
2. ^ Schatz, H.; A. Aprahamian, V. Barnard, L. Bildsten, A. Cumming, M. Ouellette, T. Rauscher, F.-K. Thielemann, and M. Wiescher (April 2001). "End Point of the rp Process on Accreting Neutron Stars". Physical Review Letters 86 (16): 3471–3474. DOI:10.1103/PhysRevLett.86.3471. Retrieved on 2006-08-24. 
3. ^ Tuli, Jagdish K. (2005). Nuclear Wallet Cards, 7th Ed., National Nuclear Data Center. Retrieved on 2007-08-16. 


 •  • [ e]
Nuclear processes
Radioactive decayAlpha decay Beta decay Gamma radiation Cluster decay Double beta decay Double electron capture Internal conversion Isomeric transition Spontaneous fission
Other processesEmission processes: Neutron emission Positron emission Proton emission
Capturing: Electron capture Neutron capture
Stellar nucleosynthesis pp-Chain CNO cycle α process Triple-α Carbon burning Ne burning O burning Si burning R-process S-process P-process Rp-process
A seed nucleus is an isotope that is the starting point for any of a variety of fusion chain reactions. The mix of nuclei produced at the conclusion of the chain reaction generally depends strongly on the relative availability of the seed nucleus or nuclei and the component being
..... Click the link for more information.
Nucleosynthesis is the process of creating new atomic nuclei from preexisting nucleons (protons and neutrons). The primordial nucleons themselves were formed from the quark-gluon plasma of the Big Bang as it cooled below ten million degrees.
..... Click the link for more information.
The S-process or slow-neutron-capture-process is a nucleosynthesis process that occurs at relatively low neutron density and intermediate temperature conditions in stars. Under these conditions the rate of neutron capture by atomic nuclei is slow relative to the rate of radioactive
..... Click the link for more information.
The r-process is a nucleosynthesis process occurring in core-collapse supernovae (see also supernova nucleosynthesis) responsible for the creation of approximately half of the neutron-rich atomic nuclei that are heavier than iron.
..... Click the link for more information.
129: 312.
..... Click the link for more information.
4, 6
(mildly acidic oxide)
Electronegativity 2.1 (scale Pauling)
Ionization energies
(more) 1st: 869.3 kJmol−1
2nd: 1790 kJmol−1
3rd: 2698 kJmol−1
..... Click the link for more information.
Alpha decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (two protons and two neutrons bound together into a particle identical to a helium nucleus) and transforms (or 'decays') into an atom with a mass number 4 less and atomic number 2 less.
..... Click the link for more information.
4, 6
(mildly acidic oxide)
Electronegativity 2.1 (scale Pauling)
Ionization energies
(more) 1st: 869.3 kJmol−1
2nd: 1790 kJmol−1
3rd: 2698 kJmol−1
..... Click the link for more information.
The kelvin (symbol: K) is a unit increment of temperature and is one of the seven SI base units. The Kelvin scale is a thermodynamic (absolute) temperature scale where absolute zero — the coldest possible temperature — is zero kelvins
..... Click the link for more information.
The Coulomb barrier, named after physicist Charles-Augustin de Coulomb (1736–1806), is the energy barrier due to electrostatic interaction that two nuclei need to overcome so they can get close enough to undergo nuclear fusion.
..... Click the link for more information.
The CNO cycle (for carbon-nitrogen-oxygen), or sometimes Bethe-Weizsäcker-cycle, is one of two fusion reactions by which stars convert hydrogen to helium, the other being the proton-proton chain.
..... Click the link for more information.
Proton drip line is a concept in particle and nuclear physics. An unstable atomic nucleus beyond the proton drip line will leak free protons. In other words, the proton drip line is the line on the Z, N plane (see chart of nuclides) where the proton separation energy is zero; the
..... Click the link for more information.
The weak interaction (often called the weak force or sometimes the weak nuclear force) is one of the four fundamental interactions of nature. In the Standard Model of particle physics, it is due to the exchange of the heavy W and Z bosons.
..... Click the link for more information.
The strong interaction or strong force is today understood to represent the interactions between quarks and gluons as detailed by the theory of quantum chromodynamics (QCD).
..... Click the link for more information.
In physics, the electromagnetic force is the force that the electromagnetic field exerts on electrically charged particles. It is the electromagnetic force that holds electrons and protons together in atoms, and which hold atoms together to make molecules.
..... Click the link for more information.
black hole is a region of space in which the gravitational field is so powerful that nothing can escape after having fallen past the event horizon. The name comes from the fact that even electromagnetic radiation (e.g. light) is unable to escape, rendering the interior invisible.
..... Click the link for more information.
129: 312.
..... Click the link for more information.
A red giant is a luminous giant star of low or intermediate mass that is in a later phase of its evolution, with nuclear fusion going on in a shell outside the core but not in the core itself.
..... Click the link for more information.
In astrophysics, the term accretion is used for at least two distinct processes.

The first and most common is the growth of a massive object by gravitationally attracting more matter, typically gaseous matter in an accretion disc.
..... Click the link for more information.
Gravitation is a natural phenomenon by which all objects with mass attract each other. In everyday life, gravitation is most familiar as the agency that endows objects with weight.
..... Click the link for more information.
velocity is defined as the rate of change of position. It is a vector physical quantity, both speed and direction are required to define it. In the SI (metric) system, it is measured in meters per second (m/s). The scalar absolute value (magnitude) of velocity is speed.
..... Click the link for more information.
accretion disc (or accretion disk) is a structure formed by diffuse material in orbital motion around a central body. The central body is typically either a young star, a protostar, a white dwarf, a neutron star, or a black hole.
..... Click the link for more information.
Degenerate matter is matter which has sufficiently high density that the dominant contribution to its pressure arises from the Pauli exclusion principle. The pressure maintained by a body of degenerate matter is called the degeneracy pressure
..... Click the link for more information.
Static overpressure, i.e., the sharp increase in pressure exerted by the shock wave. The overpressure at any given point is directly proportional to the density of the air in the wave.
  • Dynamic pressures, i.e.
    ..... Click the link for more information.
    • X-ray bursters are a class of binary stars which have periodic outbursts luminous in X-rays. They contain a neutron star and an accreting companion.

    Burst Astrophysics


    ..... Click the link for more information.
    digital object identifier (or DOI) is a permanent identifier given to a document, which is not related to its current location. A typical use of a DOI is to give a scientific paper or article a unique identifying number that can be used by anyone to locate details of the paper, and
    ..... Click the link for more information.
    Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves. This decay, or loss of energy, results in an atom of one type, called the parent nuclide
    ..... Click the link for more information.
    Alpha decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (two protons and two neutrons bound together into a particle identical to a helium nucleus) and transforms (or 'decays') into an atom with a mass number 4 less and atomic number 2 less.
    ..... Click the link for more information.
    beta decay is a type of radioactive decay in which a beta particle (an electron or a positron) is emitted. In the case of electron emission, it is referred to as "beta minus" (β−), while in the case of a positron emission as "beta plus" (β+).
    ..... Click the link for more information.
    For the music band, see .
    Gamma rays or gamma-ray (denoted as γ) are forms of electromagnetic radiation (EMR) or light emissions of a specific frequency produced from sub-atomic particle interaction, such as electron-positron annihilation and
    ..... Click the link for more information.

    This article is copied from an article on Wikipedia.org - the free encyclopedia created and edited by online user community. The text was not checked or edited by anyone on our staff. Although the vast majority of the wikipedia encyclopedia articles provide accurate and timely information please do not assume the accuracy of any particular article. This article is distributed under the terms of GNU Free Documentation License.