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ISOLDE Seminar

Deep Inelastic Reactions and K-Isomers in Neutron Rich Nuclei extending to the Perimeter of the A=180-190 Deformed Region

by Prof. George Dracoulis (Australian National University)

Wednesday, 11 April 2012 from to (Europe/Zurich)
at CERN ( 26-1-022 )
Description Deformed nuclei near Z = 72 and N = 104 are known to be prolific in multi-quasiparticle high-K isomers, formed by combining high-Omega orbitals near the proton and neutron Fermi surfaces. Many more are predicted to occur in stable and neutron-rich isotopes but few are accessible with conventional reactions. Multi-nucleon transfer or “deep-inelastic” reactions with heavy energetic beams offer an alternative, although non-selective, means of production, complementing to some extent, fragmentation reactions.
We have carried out a series of systematic studies extending, to date, from the well deformed Tm isotopes through the gamma-soft neutron-rich W and Os region, to some of the notionally spherical 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 as well as a few technical aspects of discovery, assignment and characterization. Selected cases will be used to illustrate emerging issues to do with isomer survival and discovery, and aspects of nuclear structure, including K-mixing, alignments and shape changes.