A new model is proposed for the mechanism of cluster formation and then penetration of the confining nuclear interaction barrier in radioactive nuclei. The cluster formation is treated as a quantum-mechanical fragmentation process and the WKB penetrability is found analytically. Applications of the model are made to ' C decay of Ra and Ne decay of~U. The branching ratio for ' C decay of U is also calculated and is found to be incredibly small as compared to that for its "Ne decay.

No abstract

For collisions between deformed and oriented nuclei, the fragmentation theory is extended for the generalized nuclear proximity potential, with deformations included up to the hexadecupole deformations. For co-planar nuclei, the orientations are shown to get optimized (uniquely fixed) by the signs of their quadrupole deformations alone, not affected by the signs of their hexadecupole deformations. The optimum orientations are obtained for both the ‘hot compact’, and ‘cold elongated’ configurations of any two colliding nuclei. The hexadecupole deformations are shown to help fusion (hot or cold), depending on the choice of the reaction partners. Calculations are made for the 208Pb- and 48Ca-induced reactions and the neighbouring deformed nuclei. The calculated fragmentation potentials for optimally oriented nuclei, compared with both nuclei taken spherical, show that the excitation energy of the potential energy minima is significantly lowered for cold (elongated) fusion of deformed nuclei, but it remains nearly the same for at least the asymmetric hot (compact) fusion reactions. A number of new minima (target–projectile combinations) arise due to the cold and nearly symmetric hot fusion of deformed, optimally oriented nuclei.

This review summarizes both the experimental and theoretical status of cluster radioactivity. The contents are: a brief introduction, the experimental methods used and the results obtained, the theories of cluster radioactivity, cluster-decay as (cold) super-asymmetric spontaneous fission, and its fine structure. The theories studied are the unified fission models (UFM), the preformed cluster models (PCM), and the comparison between empirical and theoretical preformation probabilities. A brief discussion of other theories, not studied so much in detail, is also given. An overview of this research is added at the end, pointing out, in particular, its relation to other phenomena.