Effect of increasing neutron-excess on the fusion cross-section in ¹²⁻¹⁵C + ¹²C at above-barrier energies

Fusion excitation functions at energies above the fusion barrier for ¹²⁻¹⁵C + ¹²C are examined. From these excitation functions the average fusion cross-section, <σ_F>, is calculated. For this isotopic chain, the measured dependence of <σ_F> on neutron excess is compared with static barrier penetration models. The more rapid increase observed for the experimental cross-sections above the geometric increase predicted by the static models suggests that the stronger dependence on neutron-excess measured may be attributable to dynamics. 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.