Elsevier

Nuclear Physics A

Volume 443, Issue 1, 23 September 1985, Pages 1-28
Nuclear Physics A

NpNn systematics in heavy nuclei

https://doi.org/10.1016/0375-9474(85)90318-5Get rights and content

Abstract

The systematics of the nuclear phase transitional regions near A = 100, 130, 150 and 190 are studied from the standpoint of the valence nucleon product NpNn. The use of this construction or parametrization leads to a substantial simplification of these complex regions. The results are discussed in terms of the proton-neutron interaction in different shell-model orbits and are used to interpret the effects of subshell closures. The mechanism for the onset of deformation near A = 100, involving the eradication of such a subshell closure in one type of particle as a function of the number of valence nucleons of the other type, is shown to be of more general applicability, not only for the A = 150 region, but also for the A = 190 region. The NpNn plots for five mass regions (A = 100, 130, 150 (Z ⩽ 64), 150 (Z ⩾ 66) and 190) are compared. It is found that the quantity NpNn provides an excellent unit to assess the rapidity of different transition regions: that is, the slopes of different observables plotted against this quantity are related to the average interaction strength, per proton-neutron pair, in the crucial highly overlapping orbits whose occupation induces the phase transition. The five regions studied are found to display a remarkable similarity which results from similar strengths of this interaction in the crucial orbits.

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