Low-lying dipole strength for weakly bound systems: A simple analytic estimate

A simple analytic expression is proposed for the total low-lying dipole strength observed in the break-up of weakly bound systems. The model assumes pure ldquosingle-particlerdquo transitions from the ldquohalordquo weakly bound state to continuum states treated as plane waves (neutrons) or regular Coulomb functions (protons). The analytic expression for the total strength approximately depends on the inverse of the binding energy and the reduced mass of the halo, with correction factors accounting for the charge of the halo and the finite size of the potential.