Compound Nucleus

compound nucleus

[′käm‚pau̇nd ′nü·klē·əs]
(nuclear physics)
An intermediate state in a nuclear reaction in which the incident particle combines with the target nucleus and its energy is shared among all the nucleons of the system.

Compound Nucleus


a nuclear system formed in the course of a nuclear reaction by the combination of the incident particle with the target nucleus. A compound nucleus is unstable and decays after a short period into final reaction products. The energy brought in by the incident particle is shared among the degrees of freedom of the compound nucleus, as is the case when bodies are heated. Because of statistical fluctuations, one or more nuclear particles may acquire an energy that is greater than the average energy value and that permits such particles to leave the “heated” nucleus. This process is analogous to the evaporation of a liquid and results in the decay of the compound nucleus. The mean life of a compound nucleus (10–22–10–21 sec) is many times greater than the time required by a particle to traverse the region of space occupied by the nucleus.

Nuclear reactions that proceed through the intermediate stages of the formation and decay of a compound nucleus have the following characteristics: the angular distribution of the final products is symmetric (forward-backward with respect to the direction of the incident particles in the center-of-mass system), the energy spectrum of the emitted particles is Maxwellian (seeMAXWELLIAN DISTRIBUTION), and the relative probabilities of the final channels of various reactions involving the same compound nucleus have identical values.

The notion of the compound nucleus was first advanced by N. Bohr in 1936. Ia. I. Frenkel’ suggested that a compound nucleus is analogous to a heated fluid. On the basis of these contributions, a quantitative thermodynamic theory of the compound nucleus was developed in 1936 and 1937 by H. A. Bethe, L. D. Landau, and V. F. Weisskopf.


Landau, L., and Ia. Smorodinskii. Lektsii po teorii atomnogo iadra. Moscow, 1955.
Akhiezer, A. I., and I. Ia. Pomeranchuk. Nekotorye voprosy teorii iadra. Moscow-Leningrad, 1948.
Davydov, A. S. Teoriia atomnogo iadra, 2nd ed. Moscow, 1973.
Bethe, H. A., and P. Morrison. Elementarnaia teoriia iadra. Moscow, 1958. (Translated from English.)
Weisskopf, V. Statisticheskaia teoriia iadernykh reaktsii. Moscow, 1952. (Translated from English.)
Fermi, E. Iadernaia fizika. Moscow, 1951. (Translated from English.)
Bethe, H. A. Fizika iadra, part 2. Moscow-Leningrad, 1948. (Translated from English.)
Blatt, J., and V. Weisskopf. Teoreticheskaia iadernaia fizika. Moscow, 1954. (Translated from English.)


References in periodicals archive ?
The above mentioned enhancement of the symmetry breaking effects in the neutron reactions with heavy nuclei originates from the multi-component of the nuclear compound states, namely, a big number of single particle nuclear configurations, which contribute to the excited nuclear state after compound nucleus been formed.
Finally, the compound nucleus decays with an outgoing neutron.
Finally, two years ago, researchers at England's Daresbury Laboratory created spinning dysprosium-152 by colliding calcium-48 and palladium-108 ions, which fused into a compound nucleus. Using an array of germanium detectors, they recorded the gamma rays that dysprosium-152 nuclei emit in order to cool off and slow down.
The enhancement factor of a million observed in the 1980s in compound nucleus parity violating observables stimulated great interest in searching for time reversal violation.
Our results confirm that there is a shift in the zero of the capture correlation asymmetry from the resonance energy [E.sub.p], of order ([v.sub.PT]/[v.sub.P])[GAMMA], where [v.sub.PT] is the root-mean-square (rms) value of compound nucleus matrix elements of the unknown P-odd T-odd interaction and [v.sub.P] is the rms value of compound nucleus matrix elements of the P-odd weak interaction.
b) gamma-quanta corresponding to transitions from [1.sup.+] or [1.sup.-] states of the intermediate compound nucleus to the [0.sup.+] ground state of the final nucleus.
To be of interest as a test of P-odd time reversal invariance, data on displacements of zeros in (n, [gamma]) correlations should comprise measurements at several p-wave resonances within a given compound nucleus [12].