NEUTRON HALOS AND E1 RESONANCES IN PB-208

Neutron halos and their relations to the structure of El resonances ar e examined in a microscopic random phase approximation continuum calcu lation of (208)pb. Our results predict the occurrence of small but dis tinct El peaks located in the low energy tail of the giant dipole reso nance and consisting of highly coherent neutron particle-hole excitati ons whose energy and strength are found to correspond well to photoneu tron and electron scattering data. This work suggests that the high cu rrent interest in the appearance of neutron halos in light exotic nucl ei could constructively be channeled to investigate similar occurrence s in heavier systems where model calculations have already been thorou ghly tested.