Nuclear Halo Effect on Direct Nucleon Capture Cross Sections

Abstract：

The capture cross sections at stellar energies are very difficult to be measured directly. Hence,data are usually evaluated by means of indirect methods and extrapolations from the experimental data obtained at the possible lowest energies. In this work we have shown that the results obtained with the asymptotic normalization coefficient (ANC) method are nearly model independent. Therefore, the ANC approach of the transfer reactions provides a reliable way for the determination of the capture cross sections at stellar energies. By virtue of its reliability, we have calculated the capture cross sections of the ¹⁰Be (n,γ)¹¹Be reaction by means of nuclear ANC method.¹¹Be is a well-known neutron halo nucleus with two weak bound states. As a typical example, we have shown that the radiative cross sections for a nucleon captured into a halo state are obviously enhanced. The enormous enhancement of the capture cross section is just due to the large overlap of the incident neutron wave with the extended tail of the halo.