Polarisation potential and sub-barrier fusion in a multiphonon excitation model

The authors define an adiabatic polarisation potential describing the coupling to the collective vibrational states. The corrections on the folding potential are found to be very large. Correspondingly the sub-barrier fusion cross section is strongly enhanced and, for the ⁴⁰Ca+⁴⁰Ca system, the agreement with the experimental data is good in view of the fact that they do not have any adjustable parameters. For the asymmetric ⁴⁰Ca+⁴⁸Ca case, the introduction of some other degrees of freedom, like the nucleon transfer is required.