Systematic decay studies of even-even ~(132-138)Nd, ~(144-158)Gd, ~(176-196)Hg and ~(192-198)Pb isotopes

摘要

The alpha and cluster decay properties of the ~(132-138)Nd, ~(144-158)Gd, ~(176-196)Hg and ~(192-198)Pb even-even isotopes in the two mass regions A=130-158 and A=180-198 are analyzed using the Coulomb and Proximity Potential Model. On examining the clusters at corresponding points in the cold valleys (points with same A2) of the various isotopes of a particular nucleus we find that at certain mass numbers of the parent nuclei, the clusters emitted are getting shifted to the next lower atomic number. It is interesting to see that the change in clusters appears at those isotopes where a change in shape is occurring correspondingly. Such a change of clusters with shape change is studied for the first time in cluster decay. The alpha decay half lives of these nuclei are computed and these are compared with the available experimental alpha decay data. It is seen that the two are in good agreement. On making a comparison of the alpha half lives of the normal deformed and superdeformed nuclei, it can be seen that the normal deformed ~(132)Nd, ~(176-188)Hg and ~(192)Pb nuclei are found to be better alpha emitters than the superdeformed (in excited state) ~(134,136)Nd, ~(190-196)Hg and ~(194)Pb nuclei. The cluster decay studies reveal that as the atomic number of the parent nuclei increases the N≠Z cluster emissions become equally or more probable than the N=Z emissions. On the whole the alpha and cluster emissions are more probable from the parents in the heavier mass region (A=180-198) than from the parents in the lighter mass region (A=130-158). The effect of quadrupole (β2) and hexadecapole (β4) deformations of parent and fragments on half life times are also studied.