A systematic study of the population probabilities of microsecond isomers produced following the fragmentation of ${}^{208}\mathrm{Pb}$ projectiles at 1 GeV/nucleon has been undertaken at the SIS/FRS facility at GSI Darmstadt. Gamma decays from approximately 20 isomeric states, mainly in the rare-earth and transitional nuclei with $A\sim 180,$ were identified and the corresponding isomeric ratios deduced. The results are compared with a model based on the statistical abrasion-ablation description of relativistic fragmentation and simple assumptions concerning gamma cascades in the final nucleus (sharp cutoff). The model is found to represent an upper limit for the population of isomeric states in relativistic projectile fragmentation.

• Received 29 May 2001

DOI:https://doi.org/10.1103/PhysRevC.65.064604