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

We investigate the excitation of multiphonon states in relativistic heavy-ion collisions. A semiclassical formalism is used to determine the one-step and two-step Coulomb excitation of the double-phonon GDR x GDR excitation. The excitation cross sections of the L = 0 and L = 2 states are determined separately with the use of sum rules for estimating corresponding matrix elements. The nuclear contributions to the excitation process are also calculated and shown to be small. The widths of final and intermediate states are taken into account; physical problems related to the spreading width of the double-phonon states are discussed in detail. The recent experimental data are discussed and compared to our calculations.