New look at Geiger-Nuttall law and α clustering of heavy nuclei

The Geiger-Nuttall(GN)law ofαdecay is commonly explained in terms of the quantum tunneling phenomenon.In this study,we show that such an explanation is actually not enough regarding theαparticle clustering.Such a conclusion is drawn after exploring the involved coefficients of the GN law based on the conventional description ofαdecay,namely the formation of anαcluster and its subsequent penetration.The specific roles of the two former processes,in the GN law,manifest themselves via the systematical analysis of the calculated and experimentalαdecay half-lives versus the decay energies across the Z=82 and N=126 shell closures.Theα-cluster preformation probability is then found to behave in a GN-like pattern.This previously ignored point is explicitly demonstrated as the product of an interplay between the mean-field and pairing effect,which in turn reveals the structural influence on the formation of theαcluster in a simple and clear manner.In addition to providing an effective method to evaluate the amount of surfaceαclustering in heavy nuclei,the present conjecture supports other theoretical treatments of theαpreformation probability.