Systematics of cluster decay modes

Spontaneous emission of some C, O, F, Ne, Mg, and Si isotopes, from heavy parent nuclei, have been experimentally observed since 1984, confirming earlier predictions. Experimental difficulties are mainly related to the low yield in the presence of a strong background of $\alpha$ particles. Until now, only some of the most favorable cases were investigated, leading to magic or almost magic proton and neutron numbers of daughter nuclei. We present a systematics of experimental results compared to calculations, clearly showing other possible candidates for future experiments. Universal curves may be used to estimate the expected half-lives.