Effect of neutron-excess on above-barrier fusion cross-sections in $^{12−15}$C + $^{12}$C: Evidence for increasing neutron dynamics*

Examination of the average fusion cross-section at energies above the fusion barrier for $^{12,13,14,15}$C + $^{12}$C reveals that the fusion cross-section increases more rapidly than can be simply attributed to the increased size. Comparison with static barrier penetration models suggests that dynamics are the origin of this increased cross-section. Calculations with a time-dependent Hartree-Fock model also fail to describe the observed trend suggesting that for neutron-rich nuclei, neutron dynamics may play a larger role than is presently accounted for.