Effect of energy level sequences and neutron–proton interaction on α-particle preformation probability

A realistic density-dependent nucleon–nucleon (NN  ) interaction with finite-range exchange part which produces the nuclear matter saturation curve and the energy dependence of the nucleon–nucleus optical model potential is used to calculate the preformation probability, SαSα, of α  -decay from different isotones with neutron numbers N=124,126,128,130 and 132N=124,126,128,130 and 132. We studied the variation of SαSα with the proton number, Z, for each isotone and found the effect of neutron and proton energy levels of parent nuclei on the behavior of the α  -particle preformation probability. We found that SαSα increases regularly with the proton number when the proton pair in α-particle is emitted from the same level and the neutron level sequence is not changed during the Z-variation. In this case the neutron–proton (n–p  ) interaction of the two levels, contributing to emission process, is too small. On the contrary, if the proton or neutron level sequence is changed during the emission process, SαSα behaves irregularly, the irregular behavior increases if both proton and neutron levels are changed. This behavior is accompanied by change or rapid increase in the strength of n–p interaction.