Impact of shell structure on the fusion of neutron-rich mid-mass nuclei with oxygen 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. 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 São Paulo fusion model using matter densities from systematics fails to describe the measured excitation functions. Use of more realistic densities from a Dirac-Hartree-Bogoliubov (DHB) approach performs significantly better though it still overpredicts the closed-shell nuclei.