Systematic decay studies of even-even 132−138132-138^Nd, 144−158144-158^Gd, 176−196176-196^Hg and 192−198192-198^Pb isotopes

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 analysed using the Coulomb and Proximity Potential Model. On examining the clusters at corresponding points in the cold valleys (points with same A_2) 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 super deformed 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 super deformed (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 \neq 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 ({\beta}_2) and hexadecapole ({\beta}_4) deformations of parent and fragments on half life times are also studied.Comment: 42 pages,19 figure

Dynamic coexistence of various configurations: clusters vs.nuclei

The presence of energy shells in metallic clusters and atomic nuclei leads to a peculiar relation between the number of particles N and the structure, and this leads to a strong correlation between the energy spectrum and N. An analysis of experimental data leads to the conclusion that, in addition to the static Jahn-Teller effect, the dynamic effect leading to the quantum coexistence of different configurations (quantum oscillations) plays an important role. Such suggested coexistence is an essential feature of clusters as well as nuclei, both finite Fermi systems.Comment: 6 pages, 2 figure

Astrophysics on the GRAPE Family of Special Purpose Computers

The GRAPE-4, the world's fastest computer in 1995-1997, has produced some major scientific results, through a wide diversity of large-scale simulations in astrophysics. Applications have ranged from planetary formation, through the evolution of star clusters and galactic nuclei, to the formation of galaxies and clusters of galaxies.Comment: 15 pages, to apper in Scienc