Closed-shell effects from the stability and instability of nuclei against cluster decays in the mass regions 130-158 and 180-198 -: art. no. 034321

The stability and/or instability of Nd-133-137(60), Gd-144-158(64), Hg-176-194(80), and Pb-192-198(82) parents are studied with respect to the alpha and heavy-cluster decays. The alpha-decay studies also include the heavier Pb199-210 nuclei, for reasons of spherical magic shells at Z=82 and N=126. The calculations are made by using the preformed cluster-decay model, and the obtained alpha-decay half-lives are compared with the available experimental data. Having met with a very good success for the comparisons of alpha-decay half-lives and in giving the associated known magic or submagic closed-shell structures of both the parent nuclei and daughter products, the interplay of closed-shell effects in the cluster-decay calculations is investigated. The cluster-decay calculations also give the closed shell effects of known spherical magicities, both for the parent and daughter nuclei, and further predict new (deformed) closed-shells at Z=72-74 and N=96-104 due to both the stability and instability of Hg and Pb parents against cluster decays. Specifically, a new deformed daughter radioactivity is predicted for various cluster decays of Hg186-190 and Pb-194,Pb-195 parents with the best possible measurable cases identified as the Be-8 and C-12 decays of Hg-176,Hg-177 and/or Pb-192 parents. The predicted decay half-lives are within the measurable limits of the present experimental methods. The interesting point to note is that the parents with measurable cluster-decay rates are normal deformed nuclei at the transition between normal and superdeformation.