Enhancement of fusion at near-barrier energies for neutron-rich light nuclei: 19O +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 1⁹ O +1² C and 1⁸ O +1² C . Using the ¹⁸O(d,p) reaction and the RESOLUT mass spectrometer at Florida State University, a beam of ¹⁹O was produced with an intensity of 2-4 x 10³ p/s. This beam bombarded a 100 μg/cm² 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 1⁹ O +1² C in comparison to 1⁸ O +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.

Supported by the US DOE under Grant No. DEFG02-88ER-40404.