Proton-neutron correlations above 100Sn

Proton-neutron (pn) correlations in nuclei above the Z=50 shell closure are investigated in order to understand the peculiar behaviour of the 2(+) and 4(+) states in Te and Xe isotopes. It turns out that by increasing the pn pairing interaction, which becomes important for N approximate to Z nuclei, the collectivity decreases. We thus conclude that the ratio between the B(E2) value and 2(+) energy is a "fingerprint" of pn collectivity. The available experimental data indeed indicate an enhanced pn pairing interaction by also approaching double magic Z=N=20 and Z=N=28 regions. It is known that the a-particle reduced width has the largest values in the region above Sn-100. In order to reproduce the reduced alpha-decay width we use an additional pocket-like surface potential in the single particle mean field, simulating four-body correlations. 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 pn pairing correlations have a small influence on this dependence and therefore cannot explain the larger reduced decay widths above Sn-100.