Fusion and neutron transfer cross sections for 9Be+12C at sub-Coulomb energies

The energy dependence of the fusion cross section for 9Be+12C has been measured over the range Esub(c.m.)=2.8-6.3 MeV by detecting γ-rays from the various possible residual nuclei with two large NaI(Tl) detectors placed close to the target. The single-neutron transfer reactions 9Be(12C, 13C)8Be leading to the 3.088 MeV (1/2+) and 3.854 MeV (5/2+) states of 13C were measured over the range Esub(c.m.)=1.0-5.8 MeV and 2.1-5.8 MeV, respectively by detecting the characteristic γ-rays with a Ge(Li) detector. The energy dependence of the 9Be(12C, 13C1)8Be transfer cross section was found, in the sub-Coulomb energy region, to be in good agreement with the simple calculation proposed by Switkowski et al. The fusion cross sections for 9Be+12C are compared with the optical model calculations, using various parameter sets, and with experimental results for other light-nuclei systems. The fusion cross sections for 9Be+12C, 12C+13C and 9Be+16O are found to be enhanced with respect to other systems at incident energies below the Coulomb barrier. It is suggested that a loosely bound neutron fosters, via polarisation, the fusion of the two nuclei at energies just below the Coulomb barrier. (Auth.)