EVIDENCE FOR 2-PHONON GIANT-DIPOLE EXCITATION FROM INCLUSIVE MEASUREMENTS OF AU-197 TARGET DISSOCIATION

Cross sections for the electromagnetic dissociation of Au-197 targets by 1.7 A GeV Ne-20 and 1 A GeV Kr-86, Au-197 and Bi-209 beams have bee n measured by an activation method. Weizsacker-Williams calculations s how that the experimental ln cross sections can be understood by first order excitation of the giant dipole and the isoscalar giant quadrupo le resonance. In contrast, the 3n cross sections show a much stronger Z(proj)- dependence, which can only be explained by a dominant contrib ution from two-phonon giant dipole excitation.