EXCITATION OF MULTIPHONON GIANT-RESONANCE STATES IN RELATIVISTIC HEAVY-ION COLLISIONS

We investigate the excitation of multiphonon states in relativistic he avy-ion collisions. A semiclassical formalism is used to determine the one-step and two-step Coulomb excitation of the double-phonon GDR x G DR excitation. The excitation cross sections of the L = 0 and L = 2 st ates are determined separately with the use of sum rules for estimatin g corresponding matrix elements. The nuclear contributions to the exci tation process are also calculated and shown to be small. The widths o f final and intermediate states are taken into account; physical probl ems related to the spreading width of the double-phonon states are dis cussed in detail. The recent experimental data are discussed and compa red to our calculations.