New isotopes and isomers produced by the fragmentation of U-238 at 1000 MeV/nucleon

Seven previously unobserved neutron-rich isotopes (Hg-209, Hg-210, Tl-211,T l- 212, Bi-218, Po-219 and Po-220) have been identified among the fragmenta tion products of a 1000 MeV/nucleon U-238 beam incident on a beryllium targ et. The gamma-ray decays of 9 known and 4 new mu s-isomers in nuclei around Pb-208 were also observed. Production cross sections and probabilities for populating isomeric states in the fragmentation reaction were determined a nd compared with a simple model based on the statistical abrasion-ablation approach. (C) 1998 Elsevier Science B.V. All rights reserved.