By J.W. Negele, Erich W. Vogt
This quantity comprises significant articles, one delivering a old retrospective of 1 of the nice triumphs of nuclear physics within the 20th century and the opposite delivering a didactic advent to 1 of the quantitative instruments for realizing robust interactions within the twenty-first century. this article is appropriate just for complicated graduate classes in nuclear physics.
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Additional info for Advances in Nuclear Physics, Volume 27 (Advances in the Physics of Particles and Nuclei)
It is in this aspect that the shell model still “lacks theoretical foundation”. A more serious argument against the shell model for nuclei was raised by Niels Bohr. In a paper published in Nature, Bohr (1936) wrote: “It is, at any rate, clear that the nuclear models hitherto treated in detail are unsuited to account for the typical properties of nuclei for which, as we have seen, energy exchanges between the individual nuclear particles is a decisive factor. ” In the shell model, a nucleon moves in an orbit which is essentially undisturbed by the interaction with other nucleons.
It is based on nucleon-nucleon interactions which are due to a potential (“Wigner force”) or a potential multiplied by a space exchange operator (“Majorana force”). Eigenstates of Hamiltonians with such interactions could be classified according to irreducible representations of the SU(4) group. This theory was used in pre-1949 years and could account for some important properties of nuclei, like symmetry energy. A particularly attractive feature of this theory was the clear distinction between favoured (“allowed”) and unfavoured (“super-allowed”) beta decays.
The rules of coupling that Mayer suggested are very simple. In atoms, where LS-coupling prevails, Hund’s rule of coupling is that in the configuration, the lowest state has the maximum value of spin S. Such states have maximum symmetry in electron spins and hence, minimum spatial symmetry and therefore, minimum repulsion of the electrons. Among all states with maximum S, the lowest has the highest value of the total orbital angular momentum L. In nuclei, the interaction is mostly attractive and relevant coupling rules for were not known.