Andreas Görgen INTC Shape Transitions and Coexistence in Neutron-Deficient Rare Earth Isotopes A. Görgen 1, F.L. Bello Garrote 1, P.A. Butler 2, J. Cederkäll 3, E. Clément 4, J.-P.Delaroche 5, L. Gaffney 2, M. Girod 5, M.S. Guttormsen 1, T.W. Hagen 1, P. Hoff 6, D.G. Jenkins 7, J. Jolie 8, M. Klintefjord 1, W. Korten 9, A.C. Larsen 1, J.Ljungvall 10, G. O'Neill 2, P. Reiter 8, E. Sahin 1, M.-D. Salsac, S. Siem 1, N. Warr 8, M. Zielinska 9 1 Department of Physics, University of Oslo, Norway 2 Oliver Lodge Laboratory, University of Liverpool, United Kingdom 3 Department of Physics, Lund University, Sweden 4 GANIL, Caen, France 5 CEA-DIF, Bruyères-le-Châtel, France 6 Department of Chemistry, University of Oslo, Norway 7 Department of Physics, University of York, United Kingdom 8 Institut für Kernphysik, Universität zu Köln, Germany 9 CEA Saclay, IRFU/SPhN, France 10 CSNSM, CNRS-IN2P3, Orsay, France

Andreas Görgen INTC Prolate Oblate Regions of shape transitions and coexistence  measurement of collective properties  stringent test of nuclear structure theory Regions of shape transitions and coexistence  measurement of collective properties  stringent test of nuclear structure theory Experimental:  Lifetime measurements  B(E2)  Coulomb excitation  B(E2), Q s Experimental:  Lifetime measurements  B(E2)  Coulomb excitation  B(E2), Q s M.Bender et al. PRC 69, (2004) A.N.Andreyev et al. Nature 405, 430 (2000) ground-state deformation Gogny HFB

Andreas Görgen INTC Prolate Oblate Regions of shape transitions and coexistence  measurement of collective properties  stringent test of nuclear structure theory Regions of shape transitions and coexistence  measurement of collective properties  stringent test of nuclear structure theory Experimental:  Lifetime measurements  B(E2)  Coulomb excitation  B(E2), Q s Experimental:  Lifetime measurements  B(E2)  Coulomb excitation  B(E2), Q s ground-state deformation Gogny HFB configuration mixing calculation GCM(GOA) 5-dimensional (q 20,q 22, , ,  ) Gogny D1S interaction M.Girod, J.-P.Delaroche CEA Bruyères-le-Châtel Calculations predict transition from prolate to oblate shape with increasing proton number along N=78 Calculations predict transition from prolate to oblate shape with increasing proton number along N=78

Andreas Görgen INTC configuration mixing calculation GCM(GOA) 5-dimensional (q 20,q 22, , ,  ) Gogny D1S interaction M.Girod, J.-P.Delaroche CEA Bruyères-le-Châtel Calculations predict transition from prolate to oblate shape with increasing proton number along N=78 Calculations predict transition from prolate to oblate shape with increasing proton number along N=78 no experimental B(E2) values low-lying (0 + ) state  indication for shape coexistence ?  excited band built on different shape ? no experimental B(E2) values low-lying (0 + ) state  indication for shape coexistence ?  excited band built on different shape ? experiment B(E2) values in e 2 fm 4 no experimental B(E2) values  low-lying excited 0 + state ?   -vibrational band built on oblate shape ? unusual ! no experimental B(E2) values  low-lying excited 0 + state ?   -vibrational band built on oblate shape ? unusual ! 142 Gd

Andreas Görgen INTC Gd Eu Gd  h 11/2 2 h 11/2 22 1 ns 3.4 ns Sm ns19.4 ns (11/2  ) (15/2  ) (19/2  ) (23/2  ) Pm  h 11/ /2  /2  (19/2  ) 141 Sm h 11/2 11 22  h 11/2 2 indirect evidence for shape coexistence at higher spins ?? poor understanding of low-spin structure need to measure B(E2) and quadrupole moments need to measure B(E2) and quadrupole moments

Andreas Görgen INTC IS495 (July 2012 – 12 shifts): Coulomb excitation: 140 Sm + 94 Mo at 2.85 MeV/u MINIBALL + CD Si detector RILIS + new GdB 6 low-work function cavity M. Klintefjord et al. Univ. Oslo to be published 4 +  2 + (0 + )  Mo 2 +  0 + normalize to excitation of 94 Mo target nucleus (known matrix elements) 94 Mo 2 +  Mo laser ON laser OFF no beam contaminants intensity: 5  10 5 pps no beam contaminants intensity: 5  10 5 pps

Andreas Görgen INTC IS495 (July 2012 – 12 shifts): Coulomb excitation: 140 Sm + 94 Mo at 2.85 MeV/u MINIBALL + CD Si detector RILIS + new GdB 6 low-work function cavity M. Klintefjord et al. Univ. Oslo to be published 4 +  2 + (0 + )  Mo 2 +  0 + complementary lifetime measurement B(E2) values independent of Q s HIL Warsaw 2013  enhance sensitivity to Q s B(E2) QsQs 4+4+ (0 + ) B(E2) QsQs

Andreas Görgen INTC (0 + ) B(E2) QsQs 4+4+ (0 + ) B(E2) QsQs new HIE–ISOLDE experiment: Coulomb excitation of 140 Sm on 208 Pb at 4.7 MeV/u  extend B(E2) and Q s to higher-lying states in particular: second 2 + state  Q s (2 1 + )  Q s (2 2 + ) test of shape coexistence hypothesis  measure  (E0)  back detector of T-REX (1mm sufficient to stop 990 keV electrons)  SPEDE (needs further investigation) excitation cross sections for 140 Sm Pb  experimental excitation energies  matrix elements from theory large gain for multi-step excitation for higher beam energies from HIE-ISOLDE large gain for multi-step excitation for higher beam energies from HIE-ISOLDE  differential measurement: d  /d  (  cm )  together with IS495: d  /d  (Z target )  differential measurement: d  /d  (  cm )  together with IS495: d  /d  (Z target ) 12 shifts of 140 Sm beam

Andreas Görgen INTC experimental energies theoretical B(E2) next step:  Coulomb excitation of 142 Gd goal:  measure sign of Q s (2 1 + ) shape transition from 140 Sm ?  shape transition within ground-state band ?  B(E2) values  search for low-lying 0 + state and Q s  excitation probabilities requires beam development:  laser ionization scheme exists but not tested at ISOLDE  beam intensity and purity to be tested requires beam development:  laser ionization scheme exists but not tested at ISOLDE  beam intensity and purity to be tested 142 Gd Pb at 4.7 MeV/u 2.5  10 4 pps 1 mg/cm Pb 12 shifts GEANT simulation

Andreas Görgen INTC Summary:Coulomb excitation: 140 Sm Pb at 4.7 MeV/u  extend B(E2) and Q s to higher-lying states  Q s (2 1 + )  Q s (2 2 + ) test of shape coexistence hypothesis  measure  (E0) expected intensity: 5  10 5 pps 12 shifts Coulomb excitation: 142 Gd Pb at 4.7 MeV/u  measure quadrupole moments  shape transition along N=78 ?  shape transition within GSB ? expected intensity: 2.5  10 4 pps 12 shifts

Andreas Görgen INTC supplementary material

Andreas Görgen INTC  multi-step Coulomb excitation at GANIL  differential measurement:  (  )  74 Kr Pb at 4.7 MeV/u with 10 4 pps E. Clément et al., Phys. Rev. C 75, (2007) 14 transitional 5 diagonal ME