Localisation and alpha radioactivity.

Relativistic energy density functional approaches are known to well describe nuclear states which involve alpha clusters. Here, the alpha preformation probability is analysed through the behavior of the spatial localization of nucleonic states calculated with an axially deformed RHB approach over the nuclear chart. The systematic occurrence of more localised valence states, having a n=1 radial quantum number, allows to pinpoint nuclei in agreement with experimentally known alpha emitters. The cases of $^{212}$Po and $^{104}$Te are investigated, showing the concomitant roles of the pseudospin symmetry and the presence of n=1 states on the alpha preformation probability. A phenomenological law relating this probability to the radial quantum number of the valence states is also derived, allowing to describe the impact of shell effects on this probability over isotopic and isotonic chains. Finally the behavior of the alpha preformation factor is also analysed on several isotopic chains.