ELECTROMAGNETIC FISSION OF U-238 AT 600 AND 1000 MEV PER NUCLEON

Electromagnetic fission of U-238 projectiles at E/A = 600 and 1000 MeV was studied with the ALADIN spectrometer at the heavy-ion synchrotron SIS. Seven different targets (Be, C, Al, Cu, In, Au and U) were used. By considering only those fission events where the two charges added up to 92, most of the nuclear interactions were excluded. The nuclear contributions to the measured fission cross sections were determined b y extrapolating from beryllium to the heavier targets with the concept of factorization. The obtained cross sections for electromagnetic fis sion are well reproduced by extended Weizsacker-Williams calculations which include E1 and E2 excitations. The asymmetry of the fission frag ments' charge distribution gives evidence for the excitation of the do uble giant-dipole resonance in uranium.