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Proton emission

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From Wikipedia, the free encyclopedia

Type of radioactive decay

"Proton radioactivity" redirects here. For hypothetical decay of protons into subatomic particles, seeProton decay.

The decay of a proton rich nucleus A populates excited states of a daughter nucleus B by β+ emission or electron capture (EC). Those excited states that lie below the separation energy for protons (Sp) decay by γ emission towards the ground state of daughter B. For the higher excited states a competitive decay channel of proton emission to the granddaughter C exists, called β-delayed proton emission.

Nuclear physics

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Models of the nucleus Liquid drop Nuclear shell model Interacting boson model Ab initio
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Nuclear stability Binding energy p–n ratio Drip line Island of stability Valley of stability Stable nuclide
Radioactive decay Alpha α Beta β 2β 0v β⁺ K/L capture Isomeric Gamma γ Internal conversion Spontaneous fission Cluster decay Neutron emission Proton emission Decay energy Decay chain Decay product Radiogenic nuclide
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Capturing processes electron 2× neutron s r proton p rp
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Proton emission (also known asproton radioactivity) is a rare type of radioactive decay in which aproton is ejected from anucleus. Proton emission can occur from high-lying excited states in a nucleus following abeta decay, in which case the process is known as beta-delayed proton emission, or can occur from the ground state (or a low-lyingisomer) of very proton-rich nuclei, in which case the process is very similar toalpha decay.^{[citation needed]} For a proton to escape a nucleus, the proton separation energy must be negative (Sp < 0)—the proton is therefore unbound, andtunnels out of the nucleus in a finite time. The rate of proton emission is governed by the nuclear, Coulomb, and centrifugal potentials of the nucleus, where centrifugal potential affects a large part of the rate of proton emission. Thehalf-life of a nucleus with respect to proton emission is affected by the proton energy and its orbital angular momentum.^[1] Proton emission is not seen in naturally occurring isotopes; proton emitters can be produced vianuclear reactions, usually usinglinear particle accelerators.

Although prompt (i.e. not beta-delayed) proton emission was observed from an isomer incobalt-53 as early as 1969, no other proton-emitting states were found until 1981, when the proton radioactive ground states oflutetium-151 andthulium-147 were observed at experiments at theGSI in West Germany.^[2] Research in the field flourished after this breakthrough, and to date more than 25 isotopes have been found to exhibit proton emission. The study of proton emission has aided the understanding of nuclear deformation, masses, and structure, and it is a pure example ofquantum tunneling.

In 2002, the simultaneous emission of two protons was observed from the nucleusiron-45 in experiments at GSI and GANIL (Grand Accélérateur National d'Ions Lourds atCaen).^[3] In 2005 it was experimentally determined (at the same facility) thatzinc-54 can also undergo double proton decay.^[4]

References

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^Poenaru, Dorin N.; Rebel, Heinigerd; Wentz, Jürgen, eds. (2001).Nuclei Far from Stability and Astrophysics. Dordrecht: Springer Netherlands. pp. 79–81.doi:10.1007/978-94-010-0708-5.ISBN 978-0-7923-6937-0.
^S. Hofmann (1996). "Chapter 3: Proton radioactivity". In Dorin N. Poseru (ed.).Nuclear Decay Modes. Bristol: Institute of Physics Publishing. pp. 143–203.ISBN 0-7503-0338-7.
^Armand, Dominique (June 6, 2002)."A new mode of radioactive decay".CNRS. Archived fromthe original on 4 February 2005. Retrieved2022-01-07.
^Blank, Bertram; Ploszajczak, Marek (December 17, 2013). "Two-proton radioactivity".Reports on Progress in Physics.71 (4) 046301.arXiv:0709.3797.doi:10.1088/0034-4885/71/4/046301.S2CID 119276805.