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, S-alpha, of alpha-decay from different isotones with neutron numbers N = 124, 126, 128, 130 and 132. We studied the variation of S-alpha 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 alpha-particle preformation probability. We found that S-alpha increases regularly with the proton number when the proton pair in alpha-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, S-alpha 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. (C) 2013 Elsevier B.V. All rights reserved.