Expectations for 12C and 16O induced fusion cross sections at energies of astrophysical interest

The extrapolations of cross sections for fusion reactions involving 12C and 16O nuclei down to energies relevant for explosive stellar burning have been reexamined. Based on a systematic study of fusion in heavier systems, it is expected that a suppression of the fusion process will also be present in these light heavy-ion systems at extreme sub-barrier energies due to the saturation properties of nuclear matter. Previous phenomenological extrapolations of the S factor for light heavy-ion fusion based on optical model calculations may therefore have overestimated the corresponding reaction rates. A new ''recipe'' is proposed to extrapolate S factors for light heavy-ion reactions to low energies taking the hindrance behavior into account. It is based on a fit to the logarithmic derivative of the experimental cross section which is much less sensitive to overall normalization discrepancies between different data sets than other approaches. This method, therefore, represents a significant improvement over other extrapolations. The impact on the astrophysical reaction rates is discussed