Beyhan BASTIN IKS-KULeuven

1. Shape coexistence measurements in even-evenneutron-deficient Polonium isotopes by Coulomb excitation,using REX-ISOLDE and the Ge MINIBALL arrayProposal to the INTC Committee Beyhan BASTIN IKS-KULeuven Nuclei of interest Shape coexistence Vibrational-like Aim : measure the Coulomb excitation differential cross sections  Deduce transitional and diagonal matrix elements

2. Shape coexistence measurements in even-evenneutron-deficient Polonium isotopes by Coulomb excitation,using REX-ISOLDE and the Ge MINIBALL arrayProposal to the INTC Committee Argonne National Laboratory, U.S.A. R.V.F. Janssens, M. Carpenter, F. Kondev CEA-DAM, France B. Laurent CERN-ISOLDE, Switzerland J. Cederkäll, P. Delahaye, A. Dorsival, L. Fraile, J. Van de Walle, D. Voulot, F. Wenander GANIL-Caen, France E. Clément HIL University of Warsaw, Poland K. Hadynska, J. Iwanicki, P.J. Napiorkowski, J. Srebrny, K. Wrzosek, M. Zielinska KU Leuven, Belgium A. Andreyev, B. Bastin, N. Bree, T.E. Cocolios, J. Diriken, M Huyse, O. Ivanov, N. Patronis and P. Van Duppen LPCCaen, France L. Achouri, F. Delaunay, M. Marquès, N.A. Orr TU-München, Germany T. Behrens, V. Bildstein, T. Fästermann, R. Gernhäuser, Th. Kröll, R. Krücken, M. Mahgoub, P. Maierbeck, K. Wimmer University of Edinburgh, United Kingdom T. Davinson, P. Woods University of Jyväskylä, Finland P.T. Greenlees, P. Jones, R. Julin, S. Juutinen, P. Peura, P. Rahkila University of Liverpool, United Kingdom P.A. Butler, T. Grahn, R.-D. Herzberg, D.T. Joss, R.D. Page, E.S. Paul, J. Pakarinen, A. Petts, M. Scheck University of Maryland, U.S.A. I. Stefanescu University of York, United Kingdom D.G. Jenkins, A. Robinson

3. Shape coexistence measurements in even-evenneutron-deficient Polonium isotopes by Coulomb excitation,using REX-ISOLDE and the Ge MINIBALL arrayProposal to the INTC Committee • Physics motivation • Energy systematics of Po • Theoretical calculations • Remaining questions • 2) 198,200,202Po Coulomb excitation • Yields and contamination • Experimental method • Count rates and beam time request

4. p Adapted from R. Julin et al., J. Phys. G 27 (2001) R109. « regular seniority- type regime » 1) Physics motivation : energy systematics of Po (p1h9/2)2

5. p Adapted from R. Julin et al., J. Phys. G 27 (2001) R109. « regular seniority- type regime » 1) Physics motivation : energy systematics of Po Change in the mean square charge radii (p1h9/2)2 199Po T.E. Cocolios, Ph.D. thesis work, University of Leuven, to be published.

6. p Adapted from R. Julin et al., J. Phys. G 27 (2001) R109. • Particle-Core model : • A. Maj et al., Nucl. Phys. A 509 (1990) 413. • J.A. Cizewski et al., Z.Phys. A 358 (1997) 133. • 200-208Po :2 valence protons coupled to a vibrating Pb core BUT : not a good description of 02+ and for A<200 • 190-198Po :described by introducing an unphysical sharp rise in the p-core interaction parameter « regular seniority- type regime » Deformed structure Shape coexistence 1) Physics motivation : theoretical calculations (p1h9/2)2 A.M. Oros et al., Nucl. Phys. A 645 (1999) 107 cannot describe using an anhormonic vibrator framework • Beyond Mean field : • N.A. Smirnova, Phys. Lett. B 569 (2003) 151 • 0+ states :not a well defined de-formation (shapes strongly mixed) T. Grahn et al., Phys. Rev. Lett. 97 (2006) 062501. T. Grahn et al., Nucl. Phys. A 801 (2008) 83. P.H. Heenen, private communication. • 190-192Po :strong deformation • 196-200Po :soft character

7. The onset of the deformation is well established experimentally 1) Physics motivation : remaining questions • Transition from « vibrational » mode to oblate/ prolate deformation? • Sign of the deformation? (never determined) • Magnitude of the mixing? • Only collectivity information on 194Po (lifetime measurement by Recoil-decay tagging) • B(E2; 2+10+1) = 90(20) W.u • B(E2; 4+12+1) = 120(40) W.u •  High collectivity of the intruder states T. Grahn et al., Phys. Rev. Lett. 97 (2006) 062501.T. Grahn et al., Nucl. Phys. A 801 (2008) 83. Shape coexistence measurements in even-mass neutron-deficient 198,200,202Po isotopes by Coulomb excitation,using REX-ISOLDE and the Ge MINIBALL arrayProposal to the INTC Committee The reduced transition matrix elements obtained will be compared to beyond mean field models(P.H. Heenen, private communication)

8. Yields already measured1.4 GeV CERN-PSB proton beam on a UCx target (50 g.cm−2) • Beam contamination (isobaric) ~5x10-6 ions /mC 2) 198,200,202Po Coulex : Yields and contamination T.E. Cocolios et al., accepted for publication in NIMB. T. Stora, private communication • - Assumptions and expected intensities on target : • - gate on beam • First 6 of 12 proton pulses (1.2s)Np=2.1013 protons per pulse • REX efficiency ~ 1% Use of RILIS to estimate beam contamination rate

9. Miniball EP 2) 198,200,202Po Coulex : experimental method 198,200,202Po 2,9 MeV/u θP target 108Pd 1.6 mg/cm2 CD-detector ED Figure : courtesy of N. Bree, Ph.D. thesis work, University of Leuven.

10. 0.28(5) 0.32(5) 0.28(5) 0.88(15) 0.79(14) 0.78(14) 0+ 2) 198,200,202Po Coulex : count rates and beam time request 2+ 2+ 4+ 4+ 4+ 0+ 2+ 726 (1.4) 625 (3.6) 611 (84) 572 (87) 434 (2.7) 554 (98) 0+ 2+ 2+ 2+ 1392 (1.2) 677 (100) 1039 (1.3) 666 (100) 605 (100) 0+ 0+ 0+ 198Po 202Po 200Po Global Best Fit for B(E2)S. Raman et al. Atomic data and Nuclear Data Tables 78 (2001)1-128 Estimation fromK. Alder et al., Rev. Mod. Phys. 28 (1956) 432.

11. 0.28(5) 0.32(5) 0.28(5) 0.88(15) 0.79(14) 0.78(14) MINIBALL efficiency 0+ 2) 198,200,202Po Coulex : count rates and beam time request 2+ 2+ 4+ 4+ 4+ 0+ 2+ 726 (1.4) 625 (3.6) 611 (84) 572 (87) 434 (2.7) 554 (98) 0+ 2+ 2+ 2+ 1392 (1.2) 677 (100) 1039 (1.3) 666 (100) 605 (100) 0+ 0+ 0+ 198Po 202Po 200Po Global Best Fit for B(E2)S. Raman et al. Atomic data and Nuclear Data Tables 78 (2001)1-128 Estimation fromK. Alder et al., Rev. Mod. Phys. 28 (1956) 432.

12. 0.28(5) 0.32(5) 0.28(5) 0.88(15) 0.79(14) 0.78(14) 0+ 2) 198,200,202Po Coulex : count rates and beam time request 2+ 2+ 4+ 4+ 4+ 0+ 2+ 726 (1.4) 625 (3.6) 611 (84) 572 (87) 434 (2.7) 554 (98) 0+ 2+ 2+ 2+ 1392 (1.2) 677 (100) 1039 (1.3) 666 (100) 605 (100) 0+ 0+ 0+ 198Po 202Po 200Po Global Best Fit for B(E2)(S. Raman et al. Atomic data and Nuclear Data Tables 78 (2001)1-128) Estimation fromK. Alder et al., Rev. Mod. Phys. 28 (1956) 432.

13. 0.28(5) 0.32(5) 0.28(5) 0.88(15) 0.79(14) 0.78(14) Activity (202Tl) = 3.8x106 < LA but T1/2=12.23 days F. Wenander, private communication 0+ 2) 198,200,202Po Coulex : count rates and beam time request 2+ 2+ 4+ 4+ 4+ 0+ 2+ 726 (1.4) 625 (3.6) 611 (84) 572 (87) 434 (2.7) 554 (98) 0+ 2+ 2+ 2+ 1392 (1.2) 677 (100) 1039 (1.3) 666 (100) 605 (100) 0+ 0+ 0+ 198Po 202Po 200Po Global Best Fit for B(E2)(S. Raman et al. Atomic data and Nuclear Data Tables 78 (2001)1-128) Estimation fromK. Alder et al., Rev. Mod. Phys. 28 (1956) 432.