The Oppenheimer–Phillips process or strip reaction is a type of

deuteron Deuterium (or hydrogen-2, symbol or deuterium, also known as heavy hydrogen) is one of two stable isotopes of hydrogen (the other being protium, or hydrogen-1). The nucleus of a deuterium atom, called a deuteron, contains one proton and one n ...

-induced

nuclear reaction In nuclear physics and nuclear chemistry, a nuclear reaction is a process in which two nuclei, or a nucleus and an external subatomic particle, collide to produce one or more new nuclides. Thus, a nuclear reaction must cause a transformatio ...

. In this process the

neutron The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons beh ...

half of an energetic deuteron (a stable

isotope Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numb ...

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...

with one proton and one neutron) fuses with a target

nucleus Nucleus ( : nuclei) is a Latin word for the seed inside a fruit. It most often refers to: *Atomic nucleus, the very dense central region of an atom * Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA Nucl ...

, transmuting the target to a heavier isotope while ejecting a proton. An example is the nuclear transmutation of carbon-12 to

carbon-13 Carbon-13 (13C) is a natural, stable isotope of carbon with a nucleus containing six protons and seven neutrons. As one of the environmental isotopes, it makes up about 1.1% of all natural carbon on Earth. Detection by mass spectrometry A mas ...

. The process allows a nuclear interaction to take place at lower energies than would be expected from a simple calculation of the

Coulomb barrier The Coulomb barrier, named after Coulomb's law, which is in turn named after physicist Charles-Augustin de Coulomb, is the energy barrier due to electrostatic interaction that two nuclei need to overcome so they can get close enough to undergo a ...

between a deuteron and a target nucleus. This is because, as the deuteron approaches the positively charged target nucleus, it experiences a charge polarization where the "proton-end" faces away from the target and the "neutron-end" faces towards the target. The fusion proceeds when the binding energy of the neutron and the target nucleus exceeds the binding energy of the deuteron itself; the proton formerly in the deuteron is then repelled from the new, heavier, nucleus.

History

An explanation of this effect was published by

J. Robert Oppenheimer J. Robert Oppenheimer (; April 22, 1904 – February 18, 1967) was an American theoretical physicist. A professor of physics at the University of California, Berkeley, Oppenheimer was the wartime head of the Los Alamos Laboratory and is oft ...

and

Melba Phillips Melba Newell Phillips (February 1, 1907 – November 8, 2004) was an American physicist and pioneer science educator. One of the first doctoral students of J. Robert Oppenheimer at the University of California, Berkeley, Phillips completed her Ph. ...

in 1935, considering experiments with the Berkeley

cyclotron A cyclotron is a type of particle accelerator invented by Ernest O. Lawrence in 1929–1930 at the University of California, Berkeley, and patented in 1932. Lawrence, Ernest O. ''Method and apparatus for the acceleration of ions'', filed: Jan ...

showing that some elements became

radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is consi ...

under deuteron bombardment.Oppenheimer, 1995, pag
192
cf. ''Note on the transmutation function for deuterons,''

and

, Phys. Rev. 48, September 15, 1935, 500-502, received July 1, 1935.

Mechanism

During the O-P process, the deuteron's positive charge is spatially polarized, and collects preferentially at one end of the deuteron's density distribution, nominally, the "proton end". As the deuteron approaches the target nucleus, the positive charge is repelled by the

electrostatic field An electric field (sometimes E-field) is the physical field that surrounds electrically charged particles and exerts force on all other charged particles in the field, either attracting or repelling them. It also refers to the physical field f ...

until, assuming the incident energy is not sufficient for it to surmount the barrier, the "proton end" approaches to a minimum distance having climbed the Coulomb barrier as far as it can. If the "neutron end" is close enough for the

strong nuclear force The strong interaction or strong force is a fundamental interaction that confines quarks into proton, neutron, and other hadron particles. The strong interaction also binds neutrons and protons to create atomic nuclei, where it is called the ...

, which only operates over very short distances, to exceed the repulsive electrostatic force on the "proton end", fusion of a neutron with the target nucleus may begin. The reaction proceeds as follows: : In the O-P process, as the neutron fuses to the target nucleus, the deuteron binding force pulls the "proton end" closer than a naked proton could otherwise have approached on its own, increasing the potential energy of the positive charge. As a neutron is captured, a proton is stripped from the complex and is ejected. The proton at this point is able to carry away more than the incident kinetic energy of the deuteron since it has approached the target nucleus more closely than what is possible for an isolated proton with the same incident energy. In such instances, the transmuted nucleus is left in an energy state as if it had fused with a neutron of negative

kinetic energy In physics, the kinetic energy of an object is the energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acc ...

. There is an upper bound of how much energy the proton can be ejected with, set by the ground state of the daughter nucleus.Friendlander, 2008, p
68-69
/ref>Blatt, 1991, pp. 508-509

Notes

References

* * * {{DEFAULTSORT:Oppenheimer-Phillips process Nuclear physics