Nuclear nucleon density distribution

The state-dependent nuclear charge density distribution, p r), can then be obtained from the particle density distributions through convolution with the charge density distributions of the single nucleons, Pp(r) and Pn(r) respectively ... 

Finally, in Sect. 6, we have briefly given some examples for physical properties or effects, which involve the nuclear charge density distribution or the nucleon distribution in a more direct way, such that the change from a point-like to an extended nucleus is not unimportant. These include the electron-nucleus Darwin term, QED effects like vacuum polarization, and parity non-conservation due to neutral weak interaction. Hyperfine interaction, i.e., the interaction between higher nuclear electric (and magnetic)... 

Another question we might pose to ourselves is whether the neutron and proton distributions in nuclei are the same Modern models for the nuclear potential predict the nuclear skin region to be neutron-rich. The neutron potential is predicted to extend out to larger radii than the proton potential. Extreme examples of this behavior are the halo nuclei. A halo nucleus is a very n-rich (or p-rich) nucleus (generally with low A) where the outermost nucleons are very weakly bound. The density distribution of these weakly bound outermost nucleons extends beyond the radius expected from the R °c A1 /3 rule. Examples of these nuclei are nBe, nLi, and 19C. The most well-studied case of halo nuclei is 1 Li. Here the two outermost nucleons are so weakly bound (a few hundred keV each) as to make the size of 11 Li equal to the size of a 208Pb nucleus (see Fig. 2.12). 

Recall that X rays are diffracted by the electrons that surround atoms, and that images obtained from X-ray diffraction show the surface of the electron clouds that surround molecules. Recall also that the X-ray diffracting power of elements in a sample increases with increasing atomic number. Neutrons are diffracted by nuclei, not by electrons. Thus a density map computed from neutron diffraction data is not an electon-density map, but instead a map of nuclear mass distribution, a "nucleon-density map" of the molecule (nucleons are the protons and neutrons in atomic nuclei). 

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... 

Our present knowledge is in terms of average density distributions. Spatial fluctuations in density may be very important in understanding nuclei. For example, one can ask to what extent two or more nucleons have a spatial correlation. By this I mean two nucleons may have a higher probability of being closer together than the distance predicted from a "mean" density. Information on the question of correlation may come from studies of nuclear sub-units (see Sect. 43 on quasi-deuteron). 

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