Fission of exotic nuclei

A new experimental technique for nuclear-fission studies has been developed at GSI, Darmstadt. Relativistic secondary projectiles are produced by fragmentation of a 1 A GeV 238U primary beam and identified in nuclear charge and mass number. The giant resonances are excited by electromagnetic interactions in a secondary lead target, and fission from excitation energies around 11 MeV is induced. The fission fragments are identified in nuclear charge, and their velocity vectors are determined. Nuclear-charge distributions and total kinetic energies have been determined for a number of neutron-deficient actinides and preactinides which were not accessible with conventional techniques. The characteristics of multimodal fission of nuclei around 226Th are systematically investigated and related to the influence of shell effects on the potential energy and on the level density between saddle point and scission. A systematic view on the large number of elemental yields measured gave rise to a new interpretation of...