Staggering behavior of the low lying excited states of even-even nuclei in a Sp(4,R) classification scheme

摘要

We implement a high order discrete derivative analysis of the low lyingcollective energies of even-even nuclei with respect to the total number ofvalence nucleon pairs N in the framework of F- spin multiplets appearing in asymplectic sp(4,R) classification scheme. We find that for the nuclei of anygiven F- multiplet the respective experimental energies exhibit a Delta N=2staggering behavior and for the nuclei of two united neighboring F- multipletswell pronounced Delta N=1 staggering patterns are observed. Those effects havebeen reproduced successfully through a generalized sp(4,R) model energyexpression and explained in terms of the step-like changes in collective modeswithin the F- multiplets and the alternation of the F-spin projection in theunited neighboring multiplets. On this basis we suggest that the observed DeltaN=2 and Delta N=1 staggering effects carry detailed information about therespective systematic manifestation of both high order alpha - particle likequartetting of nucleons and proton (neutron) pairing interaction in nuclei.PACSnumber(s):21.10.Re, 21.60.Fw