LABORATORI NAZIONALI DI LEGNARO
The region of deformed nuclei near Z = 72 and N = 104 is known to be prolific in terms of multi-quasiparticle high-K isomers, formed by combining high- orbitals near the proton and neutron Fermi surfaces. Many more are predicted to occur in stable and neutron-rich isotopes but very few are accessible by conventional fusion-evaporation reactions. Multi-nucleon transfer or “deep-inelastic” reactions with heavy energetic beams offer an alternative, although non-selective, means of production.
We have carried out a series of systematic studies extending now, from the well deformed Tm isotopes through the neutron-rich W and Os region where the nuclei become gamma-soft, to some of the Ir and Au isotopes . The results are from measurements made using 6 MeV per nucleon, pulsed and chopped 136Xe beams provided by the ATLAS facility at Argonne National Laboratory, incident on a range of enriched targets Gamma-rays were detected with Gammasphere, with 100 detectors in operation.
I will cover some of the background associated with multi-particle states, the formation of isomers, hindered transitions and associated questions of K-quantum number purity and dilution as well as some of the technical aspects of discovery, assignment and characterization. Specific cases will be used to illustrate some of the emerging issues to do with isomer survival and discovery, and aspects of nuclear structure including K-mixing, alignments and shape changes.