The First Excited States of Even-Even Nuclei

Abstract

The collective model of the nucleus, as expressed in A. Bohr's strong coupling approximation, is applied to the low levels of even-even nuclei. It yields the correct level order of the first few states, and predicts the qualitative regularities of the first excited energy surface which are observed experimentally. The approximation is shown to be much better for two or more extra nucleons than for one, but the first excited energy spacing is sensitive to second-order corrections even for many extra nucleons. Predicted nuclear distortions are larger than is reasonable (a) in the rare earth group, and (b) near doubly magic ${\mathrm{Pb}}^{208}$. An empirical way to correct for this discrepancy is to diminish the particle-to-surface coupling coefficient.