Probing the quantum-mechanical equivalent-photon spectrum for   electromagnetic dissociation of relativistic uranium projectiles
  Electromagnetic fission cross sections for the reactions U + (Be, C, Al, Cu, In, Au, U) at E/A = 0.6 and 1.0 GeV are compared to theoretical calculations using recently proposed quantum-mechanical equivalent-photon spectra. In contrast to semi-classical calculations, systematically lower cross sections are obtained that cannot reproduce the experimental results. Furthermore, we point out that the study of electromagnetic fission cross sections or electromagnetic 1-neutron removal cross sections alone cannot provide unambiguous information on the excitation of the double giant dipole resonance. 
Th. Rubehn, W. F. J. Mueller, W. Trautmann (Lawrence Berkeley National   Laboratory and GSI Darmstadt)