Proton Decay – Proton Emission

Proton and Neutron Emission
Example: Proton and Neutron Decay
Source: JANIS (Java-based Nuclear Data Information Software); The JEFF-3.1.1 Nuclear Data Library

Proton decay is a rare type of radioactive decay of nuclei containing excess protons, in which a proton is simply ejected from the nucleus. This article describes mainly spontaneous proton emission (proton decay) and does not describe decay of a free proton. Note that, a free proton (a proton not bound to nucleons or electrons) is a stable particle that has not been observed to break down spontaneously to other particles.

See also: Stability of Proton

Proton emission occurs in the most proton-rich/neutron-deficient nuclides (prompt proton emission), and also from high-lying excited states in a nucleus following a positive beta decay. Similarly as for neutron emission, the rate of emission of these neutrons following a positive beta decay is governed primarily by beta decay, therefore this emission is known as beta-delayed proton emission.

Proton Decay - Proton EmissionThe mechanism of the decay process is very similar to alpha decay. Proton decay is also a quantum tunneling process. In order to be emitted, the proton must penetrate a potential barrier. For a proton to escape a nucleus, the proton separation energy must be negative – the proton is therefore unbound, and tunnels out of the nucleus in a finite time. Some nuclei decay via double proton emission, such as 45Fe.

If a nucleus decays via proton emission, atomic and mass numbers change by one and a daughter nucleus becomes a different element. Nuclei which can decay by this mode are described as lying highly above the neutron drip line. Proton emission is not seen in naturally occurring isotopes. Proton radioactive isotopes can be produced via nuclear reactions, usually using particle accelerators.

References:

Radiation Protection:

  1. Knoll, Glenn F., Radiation Detection and Measurement 4th Edition, Wiley, 8/2010. ISBN-13: 978-0470131480.
  2. Stabin, Michael G., Radiation Protection and Dosimetry: An Introduction to Health Physics, Springer, 10/2010. ISBN-13: 978-1441923912.
  3. Martin, James E., Physics for Radiation Protection 3rd Edition, Wiley-VCH, 4/2013. ISBN-13: 978-3527411764.
  4. U.S.NRC, NUCLEAR REACTOR CONCEPTS
  5. U.S. Department of Energy, Nuclear Physics and Reactor Theory. DOE Fundamentals Handbook, Volume 1 and 2. January 1993.

Nuclear and Reactor Physics:

  1. J. R. Lamarsh, Introduction to Nuclear Reactor Theory, 2nd ed., Addison-Wesley, Reading, MA (1983).
  2. J. R. Lamarsh, A. J. Baratta, Introduction to Nuclear Engineering, 3d ed., Prentice-Hall, 2001, ISBN: 0-201-82498-1.
  3. W. M. Stacey, Nuclear Reactor Physics, John Wiley & Sons, 2001, ISBN: 0- 471-39127-1.
  4. Glasstone, Sesonske. Nuclear Reactor Engineering: Reactor Systems Engineering, Springer; 4th edition, 1994, ISBN: 978-0412985317
  5. W.S.C. Williams. Nuclear and Particle Physics. Clarendon Press; 1 edition, 1991, ISBN: 978-0198520467
  6. G.R.Keepin. Physics of Nuclear Kinetics. Addison-Wesley Pub. Co; 1st edition, 1965
  7. Robert Reed Burn, Introduction to Nuclear Reactor Operation, 1988.
  8. U.S. Department of Energy, Nuclear Physics and Reactor Theory. DOE Fundamentals Handbook, Volume 1 and 2. January 1993.
  9. Paul Reuss, Neutron Physics. EDP Sciences, 2008. ISBN: 978-2759800414.

See above:

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