Regge poles and the collective model of nuclear giant multipole resonances

Giant nuclear dipole and higher-multipole resonances may be described by a generalized Goldhaber-Teller model I, including spin-isospin (si) and compressional (c) vibrations besides the familiar isospin (i) vibrations. Their amplitudes appear as parallel ripples in a two-dimensional surface over the (E,L) plane. Sliced at L = const this gives the usual resonance plots versus excitation energy E; sliced at E = const gives resonance plots versus L(Fig. l, case of 12C electroexcitation at i00 MeV). These resonances are manifestations of Regge poles 2 which, when traced through varying E, together with