A calculation method to estimate partial half-lives for exotic radioactivities

Careful analysis of our previous semiempirical model for the cluster radioactivity of translead nuclei suggests that a simple function of some characteristics of the emitted cluster and the daughter nucleus can account for the trends observed in the half-lives of these exotic decay processes. The half-life T 1/2 is found to be expressed in terms of the atomic numbers of the product nuclei and the Q-value of the two-body disintegrating system as τ = logT 1/2(s) = (aZ C + b)(Z D/Q)1/2 + (cZ C + d), by using a unique set of four parameters a, b, c and d, their values being determined from the fitting of this expression to the available data. About 85% of measurements are reproduced within one order of magnitude, and only in 5% of cases the calculated half-lives differ from the experimental ones by more than two orders of magnitude. It is also shown that, for some selected cases of cluster emission not yet measured, the method presented here anticipates results which are comparable to the ones obtained from systematic studies, making it a useful tool for fast estimation of half-life values of exotic radioactivities.