Neutron halos andE1 resonances inPb208

Neutron halos and their relations to the structure of E1 resonances are examined in a microscopic random phase approximation continuum calculation of ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$. Our results predict the occurrence of small but distinct E1 peaks located in the low energy tail of the giant dipole resonance and consisting of highly coherent neutron particle-hole excitations whose energy and strength are found to correspond well to photoneutron and electron scattering data. This work suggests that the high current interest in the appearance of neutron halos in light exotic nuclei could constructively be channeled to investigate similar occurrences in heavier systems where model calculations have already been thoroughly tested. © 1996 The American Physical Society.