Sub-barrier fusion enhancement caused by positive Q -value four-neutron transfer*

Abstract The effect of positive Q -value four-neutron transfer (PQ4NT) on the sub-barrier capture cross sections is investigated systematically using the empirical barrier distribution (EBD2) method. For 13 fusion reactions with , the sustained neutron-pair transfer reduces barrier heights and enhances capture cross sections at sub-barrier energies. In contrast, reactions such as 18 O+ 58 Ni, which have and , exhibit no enhancement due to stalling of subsequent neutron-pair transfer after the initial 2n transfer. Incorporating PQ4NT effects into EBD2 for systems with significantly reduces the average deviation between the predicted and experimental capture cross sections (113 datasets) by 20%. In comparison with those in reactions induced by 48 Ca ( ), the neutron pickup probabilities in the quasi-elastic scattering of 40 Ca-induced reactions ( ) are considerably larger, according to the time-dependent Hartree-Fock calculations.