Stability of the superdeformed Z = 38 shell against exotic cluster decays: reinforcing and switching of shell gaps in nuclei

New nuclear structure effects concerning the stability of deformed shells are shown to be contained in exotic cluster decays. The superdeformed Z = 38, 78Sr nucleus is found to be very stable against all cluster decays whereas the neighbouring and equally deformed Z= 40, 80Zr is not so stable, at least for some clusters. This new result of a very stable deformed shape at Z(N) = 38, and not at Z(N) 40, is understood as a switching and new reinforcement shell gap effect of Z= 38 deformed shell on N = 38 deformed shell. Other important consequences of this work on cluster radioactivity and the production of new and superheavy elements are also discussed. (author)