A survey of heavy-ion fusion cross sections at extreme sub-barrier energies has been carried out for lighter systems with positive $Q$ values. A general parametrization is proposed, which describes excitation functions for a wide range of light systems at low energies. This parametrization is then applied to a calculation of excitation functions and $S$ factors for the system ${}^{16}\mathrm{O}+{}^{16}\mathrm{O}$, which has recently been investigated with various other theoretical approaches. It is suggested that this parametrization is useful for estimating sub-barrier fusion cross sections with exotic neutron-rich partners which cannot be studied in the laboratory.

• Received 2 February 2009

DOI:https://doi.org/10.1103/PhysRevC.79.044601