Influence of shell structure on the fusion of neutron-rich mid-mass nuclei

The influence of shell effects on fusion of mid-mass nuclei is explored using isotopic chains of K and Ar ions on an oxygen target. Calculation of reduced excitation functions from the measured cross-section eliminates trivial size and barrier effects. Comparison of the reduced excitation functions reveals that the fusion cross-section for the open neutron shell projectile nuclei ⁴¹K and ⁴⁵K is systematically larger than for the closed neutron shell projectiles ³⁹K and ⁴⁷K. The Sao Paulo fusion model using one-body matter densities from systematics fails to describe the measured excitation functions. Use of more realistic densities calculated within a Dirac-Hartree-Bogoliubov (DHB) approach performs significantly better though it still overpredicts the closed shell nuclei.