Coulomb Nuclear Excitation

Coulomb Nuclear Excitation 

the transition of an atomic nucleus from the unexcited (ground) state to an excited state as a result of electrostatic interaction with an incident charged particle (electrostatic interaction is described by Coulomb's law). It occurs when a target is bombarded with fast charged particles (protons, deuterons, alpha particles, and so on)

and is most pronounced in cases where the energy of the incident particle is not very high, so that Coulomb repulsion prevents it from penetrating the nucleus. Because of the long-range character of Coulomb forces, Coulomb nuclear excitation takes place at great distances between the particles and the nucleus (compared with the nuclear dimensions), at which the short-range nuclear forces are not effective.

Coulomb nuclear excitation was predicted theoretically by V. Weisskopf in 1938 and was first observed experimentally in 1953. The effective cross section of the excitation is measured either by recording the inelastic scattering of the bombarding particles or by recording the gamma quanta or conversion electrons emitted by the excited nucleus.

Since electromagnetic processes lend themselves better to theoretical description than do nuclear processes, Coulomb nuclear excitation by particles that are not very fast is an important method of studying the nucleus. It is one of the methods of nuclear spectroscopy. As a result of research on it, the energies of excitation levels of nuclei, their spins, and the probabilities of electromagnetic transitions may be determined. In addition, it has been possible to measure the electric quadrupole moment of the nucleus, as well as (by measuring the angular distribution of the gamma quanta in a magnetic field) the dipole magnetic moment of the excited nucleus.

Fast, heavy multiply charged ions are also used in experiments on Coulomb nuclear excitation. Because the penetrability of the Coulomb potential barrier is less for such particles, the excitation of nuclear levels having energies greater than 1 mega electron volt using them has been possible.

REFERENCES

Al'fa-, beta- i gamma-spektroskopiia, part 2. Edited by K. Siegbahn. Moscow, 1969. (Translated from English.)
Gamma-luchi: Sb. st. Moscow-Leningrad, 1961.

V. P. PARFENOVA