Nuclear Structure

IN a recent note in NATURE,1 Bartlett has shown that the nuclei of the light elements may be represented by a model built up of appropriate numbers of neutrons and protons arranged in independent groups about an α-particle. It seems very significant that the numbers of protons and neutrons thus assigned to the p- and d-shells are the same as those required by the Pauli Exclusion Principle for electrons. This at once suggests that quantised spins and orbital momenta are also associated with the neutrons and protons in the nucleus. From quite another point of view, Heisenberg 2 has found it necessary to assign a spin, , to the neutron.