Proton-neutron versus α-like correlations above 100Sn

It is known that the alpha particle reduced width has the largest values in the region above Sn-100, and this behavior is usually attributed to the proton-neutron correlations. To reproduce the reduced alpha-decay width we use an additional pocket-like surface potential in the single-particle mean field that simulates four-body correlations. We show that the strength of this interaction has a universal linear dependence on the experimental reduced width above the double magic nuclei Sn-100 and Pb-208. Moreover, we demonstrate that proton-neutron pairing correlations have a small influence on this dependence and therefore cannot explain the larger reduced decay widths above Sn-100. We give an indication of the possibility of detecting Sn + n alpha structures as dipole Pigmy-like resonances.