Enhancement of fusion at near-barrier energies for neutron-rich light nuclei: $^{\mathrm{19}}$O $+ \quad^{\mathrm{12}}$C

Measuring the fusion excitation function for an isotopic chain of projectile nuclei provides a sensitive test of a microscopic description of fusion. To investigate the theoretically predicted fusion enhancement for neutron-rich light nuclei, an experiment was performed to measure the fusion excitation functions for $^{\mathrm{19}}$O $+ \quad^{\mathrm{12}}$C and $^{\mathrm{18}}$O $+ \quad^{\mathrm{12}}$C. Using the $^{\mathrm{18}}$O(d,p) reaction and the RESOLUT mass spectrometer at Florida State University, a beam of $^{\mathrm{19}}$O was produced with an intensity of 2-4 x 10$^{\mathrm{3}}$ p/s. This beam bombarded a 100 $\mu $g/cm$^{\mathrm{2}}$ carbon target. Using an approach optimized for the measurement of fusion with a low-intensity beam, evaporation residues (ERs) resulting from the de-excitation of the fusion product were measured. The ERs were identified by measuring their energy and time-of-flight. At near-barrier energies, an enhancement of fusion by a factor of three has been observed for $^{\mathrm{19}}$O $+ \quad^{\mathrm{12}}$C in comparison to $^{\mathrm{18}}$O $+ \quad^{\mathrm{12}}$C. Comparison of the experimental results with the predictions of a density constrained time-dependent Hartree-Fock (DC-TDHF) model provide evidence for the importance of pairing in the fusion process.