Collectivity against nucleon transfer in sub-barrier fusion of ¹²C+^194,198Pt

Abstract

In order to determine the relative importance of the role played by inelastic excitations and transfer channels of the colliding nuclei, in near-barrier fusion enhancement, the fusion cross sections have been measured for ¹²C+^194,198Pt in the energy range of 0.9≤E/V_B≤1.2. Additional data of quasielastic and nucleon(s)-exchange cross sections have also been measured at an energy of 1.2V_B. The strength of transfer form factors required for the simplified coupled-channels calculations has been obtained from the transfer reaction measurements using a semiclassical approach and calculations based on complex WKB approximations. Coupled-reaction-channels calculations have been performed to explain the complete data set that included fusion, quasielastic, and transfer cross sections. The dominant contributions to the enhancement of fusion cross section compared to a one-dimensional barrier-penetration model arise from coupling to inelastic channels. It has been shown for the first time that the lighter isotope (¹⁹⁴Pt) of a given nuclide that has a relatively larger collectivity (β_λ) and a larger neutron separation energy compared to the heavier isotope (¹⁹⁸Pt), exhibits larger enhancement of fusion cross section. The experimental fusion-barrier distributions were obtained from fusion and quasielastic scattering data.