Neutron halo slips

摘要

A ccelerator facilities that can supply beams of highly unstable, radioactive isotopes are making it possible to study nuclear reactions that occur naturally only in violent cosmic events such as super-novae, but which determine many of the elemental and isotopic abundances found on Earth. Some of the most neutron-rich of these nuclei have a diffuse neutron cloud that extends to large distances beyond the compact nuclear core. Based on the lessons learned from the fusion of stable nuclei, this halo might be expected to enhance, many times over, the probability of nuclear fusion at low energies. But, on page 823 of this issue, Raabe and colleagues describe an ingenious measurement that shows no such enhancement, indicating that the behaviour of the . neutron halo is more unusual than expected.