Coupled-channel effects on heavy-ion sub-barrier fusion within the doorway expansion method

Coupled-channel effects on the heavy-ion sub-barrier fusion cross section σF are investigated with the doorway expansion method. The case of two coupled channels is considered in detail. It is found that the two-doorway approximation, which leads to a simple result for σF, is in excellent agreement with exact coupled-channel calculations. The contributions from the elastic and inelastic channels to the enhanced fusion cross section are discussed. 10 refs., 4 figs