SU(2,1) Model of Multiple Giant Dipole Resonance Coulomb Excitation

We construct a three-dimensional analytically soluble model of the nonlinear effects in Coulomb excitation of multiphonon giant dipole resonances (GDR) based on the SU(2,1) algebra. The full three-dimensional model predicts enhancement of the double GDR (DGDR) cross sections at high bombarding energies. Enhancement factors for DGDR measured in 13 different processes with various projectiles and targets at different bombarding energies are well reproduced with the same value of the nonlinearity parameter with the exception of the anomalous case of 136Xe which requires a larger value.