Cluster decays

The recently discovered cluster radioactivities, intermediate decays between alpha decay and fission, i.e. spontaneous emission of carbon, oxygen, neon, magnesium and silicon, are discussed in terms of two extreme approaches: as alpha-decay-like or fission-like theories. It is shown that the phenomenological formulations, which reproduce the present experimental data well, give little information on nuclear structure but are very useful in predicting new decay modes. Microscopic descriptions are limited only to very simple cases. A new interpretation of cluster decays as a new large-amplitude collective motion is presented, which leads to a new coexistence model consisting of the usual shell model and a cluster-like model describing a soliton moving on the nuclear surface. The corresponding amplitudes describe the experimental spectroscopic factors excellently. In addition, cold fission as the emission of deformed fragments and cold fusion as the inverse process of decay for the synthesis of new elements are reviewed. A new road to the true spherical superheavy elements is indicated. (author)