 nuclei is small. Consequently, it is the interaction between the two low-density tails of the colliding nuclei that governs whether the fusion occurs. As the A$^{1/3}$ dependence does not describe the behavior of the low-density tail it is unsurprising that the experimental data deviates from this behavior.

Near and below the barrier, one expects the cross-section to be governed by the detailed shape of the barrier. Within the context of the Wong formalism this is reflected by the barrier curvature, $\hbar$$\omega$. Shown in the inset of Fig. \[fig:xs\_ratio\] is the curvature of the barrier for $^{18,19}$O + $^{12}$C as compared to $^{16}$O + $^{12}$C as a function of additional neutrons. It is clearly evident that while the additional two neutrons in $^{18}$O as compared to $^{16}$O do not substantially alter the barrier curvature, the presence of the additional unpaired neutron in $^{19}$O significantly increases the barrier curvature. The barrier in the case of $^{19}$O is a factor of 2.2 thinner than in the case of $^{16}$O resulting in greater penetration and an enhancement of the fusion cross-section. Although the success of static models in describing the fusion of stable light nuclei is well established, it is unclear whether fusion of neutron-rich nuclei necessitates consideration of collective modes i.e. dynamics as the two nuclei fuse. Comparison of the present experimental data with more sophisticated models such as a density constrained TDHF model [@Keser12] are presently underway.

In summary, we have measured for the first time the fusion of $^{19}$O + $^{12}$C at incident energies near and below the barrier. This measurement probes the open question of whether fusion of light neutron-rich nuclei is enhanced relative to their $\beta$ stable isotopes. Comparison of the fusion excitation function for $^{19}$O + $^{12}$C with that of $^{18}$O + $^{12}$C, clearly demonstrates that for the $^{19}$O system, fusion is significantly enhanced. Well above the barrier this enhancement is approximately 20 