Nucleon Magnetic Moment

A very small correction was estimated by Salpeter on account of the internal structure of the nucleon the possession of a magnetic moment implies a small change in the electrical potential. This correction is significant for hydrogen, but not for deuterium, since the non-Dirac parts of the magnetic moments of the proton and the neutron in the deuteron are approximately equal and opposite. The Dirac part of the proton moment contributes a negligible amount. 

Generally speaking, the density p ri —ta)-, which appears in the nuclear spin-dependent terms, does not coincide with the nucleon density relevant for the nuclear spin-independent term (see for instance also equation 26 in ref. [90]). The situation is reminiscent of the magnetic moment distribution... 

Before going into the details of nuclear structure, there is one more property of the nucleon which must be considered. Both types of angular momenta, p and Pf, as well as Aeir corresponding magnetic moments, are vector quantities. Quantum mechWcs forbids p (and consequently ) to be exactly parallel with an external field. At the same time the external field tries to pull the vector so that the plane of rotation becomes perpendicular to the field lines. The potential magnetic energy is... 

Tauber and Wu show that the magnetic moment of Li , calculated with the intermediate coupling parameter which best fits the level spectrum, is in better agreement with observation than that obtained from pure jj coupling. The multiplet splittings in Li can be accounted for, at least qualitatively, by the introduction of a tensor force component into the main interaction between nucleons instead of a spin-orbit force. 

Spectroscopic factors together with occupation probabilities and magnetic moments are basic elements needed for the understanding of nuclear structure. The spectroscopic factor S is defined as the probability to reach a final single-particle (hole) state when a nucleon is added to (or removed from) the target nucleus (correspondingly 5+, 5+ or ). The mean field approximation is a... 

The situation is complicated for nucleons as they carry both orbital angular momentum and intrinsic spin, leading to complex expressions for the g-factors. However, they can be calculated readily, and then compared to the observed values to make structural assignments. We will refer to the g-factors due to the individual nucleons as g, and to the g-factor due to the nucleus rotating as a whole as gR. Since only the protons contribute to the magnetic moment of the rotating nucleus we use gi Z/A as a good approximation [30]. 

Two points should be noted in connection with equation (18.2) firstly, the sign adopted in this equation differs from that of the corresponding equation (3.85) for electronic magnetic moments because the nucleus is positively charged and secondly, nuclear magnetic moments are typically two thousand times smaller than atomic magnetic moments since Pjj/Pg = m/M 1/1836. The nuclear g-factor, which is of the order of unity, takes account of the way the resultant nuclear moment is built up from the magnetic moments of individual nucleons. It therefore contains information about the detailed internal structure of the nucleus. 

It is necessary to note that the nature of the nucleon s magnetism is still not sufficiently clear. For instance, it is not understood why such an electrically neutral particle as a neutron nevertheless possesses a magnetic moment. 

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