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{{Short description|Type of nuclear fusion reaction}}
{{more references|date=June 2009}}
The '''Oppenheimer–Phillips process''' or '''strip reaction''' is a type of deuteron-induced ]. The '''Oppenheimer–Phillips process''' or '''strip reaction''' is a type of ]-induced ]. In this process the ] half of an energetic deuteron (a stable ] of ] with one ] and one neutron) fuses with a target ], transmuting the target to a heavier isotope while ejecting a proton. An example is the ] of ] to ].


The process allows a nuclear interaction to take place at lower energies than would be expected from a simple calculation of the ] between a deuteron and a target nucleus. This is because, as the deuteron approaches the positively charged target nucleus, it experiences a ] 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 ] from the new, heavier, nucleus.<ref name=friend68 />
In this process the ] half of an energetic ] fuses with a target ], transmuting it to a heavier ], while the ] half is ejected. An example would be the ] of ] to ].

The process is considered important because the ] is enhanced over that expected from the ] due to a polarization of the deuteron where the proton-end faces away from the incident nucleus and the neutron-end faces towards the incident nucleus during the most energetically favorable arrangement for the reaction.<ref name=friend68 />


== History == == History ==
⚫ An explanation of this effect was published by ] and ] in 1935, considering experiments with the Berkeley ] showing that some elements became ] under deuteron bombardment.<ref name=opp192>Oppenheimer, 1995, page cf. {{cite journal |title=Note on the transmutation function for deuterons |first=J. Robert |last=Oppenheimer |first2=Melba |last2=Phillips |journal=Phys. Rev. |volume=48 |year=1935 |pages=500–502 |doi=10.1103/PhysRev.48.500 }}</ref>

⚫ Explanation of this effect was published by ] and ] in 1935, considering experiments with the Berkeley ] showing that some elements became ] under deuteron bombardment.<ref name=opp192>Oppenheimer, 1995, page cf. ''Note on the transmutation function for deuterons,'' ] and ], Phys. Rev. 48, September 15, 1935, 500-502, received July 1, 1935.</ref>


==Mechanism== ==Mechanism==


⚫ During the O-P process, the deuteron's positive charge is spatially polarized, and collects preferentially at one end of the deuteron's ], nominally, the "proton end". As the deuteron approaches the target nucleus, the positive charge is repelled by the ] 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 ], 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 all fusion processes, the ] sets the requisite energy which interacting ] need to fuse. Since nuclei are always positively charged the ] is always repulsive. One way to avoid this problem is to use ] since they have no charge, the Coulomb barrier for such interactions is nil. Since isolated neutrons are unstable, the neutrons themselves must be created through other nuclear reactions. The O-P process allows for similar sorts of nuclear reactions to take place with naturally occurring stable deuterium.


:{| border="0"
⚫ During the O-P process, the deuteron's positive charge is spatially polarized, as if at one end of a ], the proton end. As the deuteron approaches the target nucleus, it is repelled by the ], converting ] to ] until, assuming the energy is not sufficient for it to surmount the barrier, the deuteron approaches to a minimum distance. Fusion proceeds when the unstable deuterated nucleus decays into daughter nuclei, normally a proton being one of the products.
|- style="height:2em;"
|{{SimpleNuclide|Deuterium|link=yes}}&nbsp;||+&nbsp;||{{SimpleNuclide|element|A|link=no}}&nbsp;||→&nbsp;||{{SimpleNuclide|Hydrogen|link=yes}}&nbsp;||+&nbsp;||{{SimpleNuclide|element|A+1|link=no}}&nbsp;||
|}


As the neutron is drawn to the target nucleus, the binding force exerted by it pulls the proton closer than it would otherwise have approached on its own. If the neutron is captured, the proton is stripped from it and is ejected by the ], and since it has half the mass of the deuteron, it can recoil with more than double the incident velocity, and may carry away more than the incident kinetic energy of the deuteron, leaving the transmuted nucleus in a state as if it had fused with a neutron of negative kinetic energy.<ref name=friend68>Friendlander, 2008, p. </ref><ref>Blatt, 1991, pp. 508-509</ref><ref>Blatt, 1991, pp. 508-509</ref> 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 ] 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 ]. There is an upper bound of how much energy the proton can be ejected with, set by the ] of the daughter nucleus.<ref name=friend68>Friendlander, 2008, p. </ref><ref name="Blatt, 1991, pp. 508-509">Blatt, 1991, pp. 508-509</ref>


==References== ==Notes==
{{reflist}} {{Reflist}}


==References==
*{{cite book *{{cite book
| title = Robert Oppenheimer: Letters and Recollections | title = Robert Oppenheimer: Letters and Recollections
Line 28: Line 29:
| publisher = ] | publisher = ]
| year = 1995 | year = 1995
| isbn = 0804726205, 9780804726207 }} | isbn = <!--0-8047-2620-5, -->9780804726207
| url = https://books.google.com/books?id=jwH4X5htJaYC&q=Oppenheimer%E2%80%93Phillips+process&pg=PA192 }}
*{{cite book * {{cite book
| title = Introduction to Radiochemistry | title = Introduction to Radiochemistry
| url = https://archive.org/details/introductiontora031115mbp
| author = ] | author = Gerhart Friedlander
| author-link = Gerhart Friedlander
| publisher = John Wiley And Sons | publisher = John Wiley And Sons
| year = 1949 | year = 1949
| isbn = 1443723096, 9781443723091 }} | isbn = <!--1-4437-2309-6, -->9781443723091 }}
*{{cite book *{{cite book
| title = Theoretical Nuclear Physics | title = Theoretical Nuclear Physics
| first = John | first = John
| last = M. Blatt | last = M. Blatt
| coauthor = Victor F. Weisskopf |author2=Victor F. Weisskopf
| edition = illustrated | edition = illustrated
| publisher = ] | publisher = ]
| year = 1991 | year = 1991
| isbn = 0486668274, 9780486668277 | isbn = <!--0-486-66827-4, -->9780486668277
| pages = 505-516 | pages = 505–516
| url = http://books.google.com/books?id=R3BzWYQqNGsC&pg=PA505&dq=Oppenheimer%E2%80%93Phillips+process&as_brr=3&hl=es }} | url = https://books.google.com/books?id=R3BzWYQqNGsC&q=Oppenheimer%E2%80%93Phillips+process&pg=PA505 }}


{{DEFAULTSORT:Oppenheimer-Phillips process}}
] ]


{{nuclear-stub}}

Latest revision as of 20:11, 9 February 2024

Type of nuclear fusion reaction

The Oppenheimer–Phillips process or strip reaction is a type of deuteron-induced nuclear reaction. In this process the neutron half of an energetic deuteron (a stable isotope of hydrogen with one proton and one neutron) fuses with a target nucleus, transmuting the target to a heavier isotope while ejecting a proton. An example is the nuclear transmutation of carbon-12 to carbon-13.

The process allows a nuclear interaction to take place at lower energies than would be expected from a simple calculation of the Coulomb barrier 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 and Melba Phillips in 1935, considering experiments with the Berkeley cyclotron showing that some elements became radioactive under deuteron bombardment.

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 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, 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:


D
 		 + 
X
 		 → 
H
 		 + 
X
 

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. There is an upper bound of how much energy the proton can be ejected with, set by the ground state of the daughter nucleus.

Notes

  1. ^ Friendlander, 2008, p. 68-69
  2. Oppenheimer, 1995, page 192 cf. Oppenheimer, J. Robert; Phillips, Melba (1935). "Note on the transmutation function for deuterons". Phys. Rev. 48: 500–502. doi:10.1103/PhysRev.48.500.
  3. Blatt, 1991, pp. 508-509

References

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