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From Magic 208 Pb to the 170 Dy Mid-Shell. Paddy Regan WNSL, Yale University, New Haven, CT and Dept. of Physics, University of Surrey, UK e-mail: p.regan@surrey.ac.uk. Outline. Rick’s thesis work (circa 1967, ‘before my time’)
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From Magic 208Pb to the 170Dy Mid-Shell Paddy Regan WNSL, Yale University, New Haven, CT and Dept. of Physics, University of Surrey, UK e-mail: p.regan@surrey.ac.uk
Outline • Rick’s thesis work (circa 1967, ‘before my time’) • A hard act to follow....heavy, neutron-rich • DIC around 194Os (shape shifters). • ISOL work, pushing the limits, 182Yb. • Isomer fragentation spectroscopy at GSI • 202Pt single particle state inversion • 190W, sub-shell closure ? • Towards 170Dy, best K-isomer and SU(3) • Future prospects with RIA and others ?
Neutron-rich isotopes between Z=66 and 82 are arguably the least studied region in the entire Segre chart to date.
Ga.Sp data (2001), Surrey, Legnaro et al. WNSL data, c. 1967 Ge arrays and HI beams allow g-g(-g) coincs. to probe yrast states to ‘high spins’ (12+ in 192Os currently) and study eg. rotational alignments. 2+2->2+1 2+2->0+1
First Identification of 182Yb: ISOL @ GSI 136Xe @ 11.4 MeV/u on 186W. Use GSI online mass-sep + tape-transport system to take A=182 isobars to Total Absorption Spectrometer (TAS). S. Al-Garni et al. Surrey/GSI/Liverpool
Yb (Z=70) X rays but lack of e- coincs? Implication: 1 min. isomer populates GSB in 182Yb. (102, 228 keV) A=182 S. Al-Garni et al. Surrey/GSI/Liverpool)
Production target Central focus, S2 Final focus, S4 primary beam Pb @ 1GeV/u dipole, Br degrader degrader MW=x,y scint catcher scint DE(Z2) scint (veto) Use FRS (or LISE3) to ID exotic nuclei. Transport some in isomeric states (TOF~ x00ns). Stop and correlate isomeric decays with nuclei id. eg. R. Grzywacz et al. Phys. Rev. C55 (1997) p1126 -> LISE C.Chandler et al. Phys. Rev. C61 (2000) 044309 ->LISE M. Pfutzner et al. Phys. Lett. B444 (1998) p32 -> FRS
Gamma-gamma analysis on 200Pt isomer (21 ns!), Caamano et al. Nucl. Phys. A682 (2001) p223c; Acta Phys. Pol. B32 (2001) p763
First id of ‘doubly mid-shell’ nucleus, 170Dy (N=104, Z=66). K=6+ isomers predicted for well deformed N=104 nuclei. TRS calcs (F.Xu) predict a very ‘stiff’, highly deformed prolate nucleus. Could be the best K-isomer? Data from M.Caamano et al. 33 ns isomer in 195Os (last stable 192Os), useful test of structure in prolate/oblate shape coexistence region. 194Os Wheldon et al. Phys. Rev. C63 (2001) 011304(R)
TRS Calcs for 170Dy (Z=66, N=104, NpNn=352) (see PHR, F. Xu et al. PRC65 (2002) 037302)
‘Best’ K-isomer in SU(3) 170Dy Phys. Rev. C65 (2002) 037302 170Dy
Other ways to get around the gamma-flash problem? Segmented germanium detectors and digital electronics for each individual segment. EURYSIS 6 x 6 germanium, Surrey/Liverpool/Darebury UK Gamma-Ray Tracking Project.