The spacing of the levels in the fine structure of alpha- and beta-ray processes and the existence of metastable nuclear states (isomers, isobars) are in contradiction with the existence of low lying levels corresponding to the rotation of the nucleus as a whole. The exchange of the nuclear constituents effected through rotation, together with the fact that the particles are not rigidly bound to equilibrium positions in the nucleus, will in some cases forbid, in other cases perturb the lowest levels, and cause the first state of excitation to lie considerably higher. Simple models illustrating these effects are discussed in II. In III an estimate is made for the position of the lowest excited level for heavy nuclei. It is found to vary inversely with the mass.

• Received 23 March 1938

DOI:https://doi.org/10.1103/PhysRev.53.778