A novel effect of the neutron halo formation is presented for the direct radiative neutron capture where a p-wave neutron is captured into an s orbit with neutron halo by emitting an E1 γ ray. As an example, an enormous enhancement is demonstrated for the cross section of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(n,γ${)}^{13}$C(1/$2^{+}$) at low energy in excellent agreement with a recent experiment. The S factor of the final state is evaluated. The inverse process, i.e., photo disintegration is discussed for an example of ${}_{}{}^{11}{}_{}{}^{}\mathrm{Be}$. A sharp but nonresonant peak near the threshold is obtained as a result of the neutron halo in its anomalous ground state.

• Received 2 September 1993

DOI:https://doi.org/10.1103/PhysRevC.49.R2289