Spectroscopic Studies of Isomers Produced in Relativistic Projectile Fragmentation and In-Flight Fission

Abstract: This thesis is based on a number of experiments performed at the FRagment Separator (FRS) at the Gesellschaft für Schwerionenforschung mbH (GSI) in Darmstadt, Germany, in which heavy-ion reactions at relativistic energies have been used to produce nuclei far from stability. In April 1999 projectile fragmentation of 208Pb at 1 GeV/nucleon was used to study so called K-isomers in the neutron-rich isotopes of Lu (Z=71) to Hg (Z=80). In December 1999, December 2001 and July 2002 neutron-rich nuclei in the 132Sn region were produced in projectile fission of 238U at an energy of 732-750 MeV/nucleon. The major aim of the work was the search for isomeric levels and the understanding of their properties based on the experimental observables and theoretical calculations. A number of new isomeric states has been populated and their lifetime measured. Other important goals were to investigave how this type of isomer studies could be optimized from an experimental point of view, and to obtain a better understanding of the role of collective nuclear properties in the reaction mechanisms involved. Indeed, this work provides the first systematic study of angular momentum population in in-flight fission.