Characterising excited states in and around the semi-magic nucleus 68Ni using Coulomb excitation and one-neutron transfer L. P. Gaffney1, F. Flavigny1, M. Zielińska2, K. Kolos4, A. N. Andreyev5, M. Axiotis6, D. L. Balabanski7, A. Blazhev8, J. Cederkäll9, T. E. Cocolios10, E. Clément11, T. Davinson12, G. De France11, H. De Witte1, D. Di Julio9, T. Duguet2, C. Fahlander9, S. J. Freeman10, G. Georgiev13, R. Gernhäuser14, A. Gillibert2, T. Grahn15, P. T. Greenlees15, L. Grente2, R. K. Grzywacz4,16, S. Harissopulos6, M. Huyse1, D. J. Jenkins5, J. Jolie8, R. Julin15, W. Korten2, Th. Kröll17, A. Lagoyannis6, C. Louchart2, T. J. Mertzimekis18, D. Miller19, D. Mücher14, P. Napiorkowski20, K. Nowak14, F. Nowacki21, A. Obertelli2, R. Orlandi1, J. Pakarinen15, P. Papadakis15, N. Patronis22, N. Pietralla17, P. Rahkila15, R. Raabe1, G. Rainovski17, E. Rapisarda3, P. Reiter8, M. D. Salsac2, M. Seidlitz8, B. Siebeck8, K. Sieja21, D. K. Sharp10, C. Sotty1, O. Sorlin11, J. Srebrny20, M. Taylor10, P. Van Duppen1, D. Voulot3, N. Warr8, R. Wadsworth5, F. Wenander3, K. Wimmer23, P. Woods12, K. Wrzosek-Lipska1 1KU Leuven, Belgium; 2CEA-Saclay, France; 3CERN-ISOLDE, Switzerland; 4University of Kentucky, U.S.; 5University of York, U.K.; 6NCSR-Demokritos, Greece; 7INRNE-BAS, Bulgaria; 8University of Köln, Germany; 9University of Lund, Sweden; 10Univeristy of Manchester, U.K.; 11GANIL, France; 12University of Edinburgh, U.K.; 13CSNSM, France; 14TU-München, Germany; 15University of Jyväskylä; Helsinki Institute of Physics, Finland; 16Oak Ridge National Laboratory, U.S.; 17TU Darmstadt, Germany; 18Univeristy of Athens, Greece; 19TRIUMF, Canada; 20HIL University of Warsaw, Poland; 21Universite de Strasbourg, France; 22University of Ioannina, Greece; 23Central Michigan University, U.S.

Characterising excited states in and around the semi-magic nucleus 68Ni using Coulomb excitation and one-neutron transfer L. P. Gaffney1, F. Flavigny1, M. Zielińska2, K. Kolos4, A. N. Andreyev5, M. Axiotis6, D. L. Balabanski7, A. Blazhev8, J. Cederkäll9, T. E. Cocolios10, E. Clément11, T. Davinson12, G. De France11, H. De Witte1, D. Di Julio9, T. Duguet2, C. Fahlander9, S. J. Freeman10, G. Georgiev13, R. Gernhäuser14, A. Gillibert2, T. Grahn15, P. T. Greenlees15, L. Grente2, R. K. Grzywacz4,16, S. Harissopulos6, M. Huyse1, D. J. Jenkins5, J. Jolie8, R. Julin15, W. Korten2, Th. Kröll17, A. Lagoyannis6, C. Louchart2, T. J. Mertzimekis18, D. Miller19, D. Mücher14, P. Napiorkowski20, K. Nowak14, F. Nowacki21, A. Obertelli2, R. Orlandi1, J. Pakarinen15, P. Papadakis15, N. Patronis22, N. Pietralla17, P. Rahkila15, R. Raabe1, G. Rainovski17, E. Rapisarda3, P. Reiter8, M. D. Salsac2, M. Seidlitz8, B. Siebeck8, K. Sieja21, D. K. Sharp10, C. Sotty1, O. Sorlin11, J. Srebrny20, M. Taylor10, P. Van Duppen1, D. Voulot3, N. Warr8, R. Wadsworth5, F. Wenander3, K. Wimmer23, P. Woods12, K. Wrzosek-Lipska1 Coulomb excitation – 68Ni 68Ni beam @ 4.0, 4.5, 5.0 MeV/u One-neutron transfer – 69Ni 70Ni beam @ 3.5 MeV/u Coulomb excitation – 70Ni 1KU Leuven, Belgium; 2CEA-Saclay, France; 3CERN-ISOLDE, Switzerland; 4University of Kentucky, U.S.; 5University of York, U.K.; 6NCSR-Demokritos, Greece; 7INRNE-BAS, Bulgaria; 8University of Köln, Germany; 9University of Lund, Sweden; 10Univeristy of Manchester, U.K.; 11GANIL, France; 12University of Edinburgh, U.K.; 13CSNSM, France; 14TU-München, Germany; 15University of Jyväskylä; Helsinki Institute of Physics, Finland; 16Oak Ridge National Laboratory, U.S.; 17TU Darmstadt, Germany; 18Univeristy of Athens, Greece; 19TRIUMF, Canada; 20HIL University of Warsaw, Poland; 21Universite de Strasbourg, France; 22University of Ioannina, Greece; 23Central Michigan University, U.S.

Monte Carlo Shell Model calculations Y. Tsunoda JPG (2013), arXiv [nucl-th] 1309.5851v1

Excited states in 68Ni (Z=28; N=40) Single-step Coulex Multi-step Coulex g-ray decays B(E2; 0+1 -> 2+1) = 3.1(4) W.u. (b,c) Re-measure B(E2; 0+1 -> 2+1) at safe energy and higher precision with respect to 196Pt target excitation. Determine if higher-order transitions are of collective nature or not, using “clean” 208Pb target. Y. Tsunoda J. Phys. G. (2013), arXiv [nucl-th] 1309.5851v1 O. Sorlin, et al., Phys. Rev. C 88, 092501 (2002) – Intermediate energy Coulomb excitation N. Bree, et al., Phys. Rev. C 78, 047301 (2008)

70Ni: A discrepancy RDDS: - - - = 2.7 W.u. ― = 10.0 W.u. x Intermediate energy Coulex gives large B(E2) = 10.0 W.u. Large B(E2) explained as proton-core polarisation (a) New RDDS Lifetime gives B(E2) = 2.7 W.u. (b) Consistent with latest shell-model calculations (c) Reproduced from: O. Sorlin & M. Porquet, Prog. Part. Nucl. Phys. 61, 602 (2008). x (b) D. Miller et al., Bull. Am. Phys. Soc. 55, DC.00001 (2010). (c) Y. Tsunoda JPG (2013), arXiv [nucl-th] 1309.5851v1. (b) RDDS: - - - = 2.7 W.u. ― = 10.0 W.u. 1259.6 keV (a) (a) O. Perru et al., Phys. Rev. Lett. 96, 232501 (2006).

Coulex experiment and simulations 68Ni on 208Pb(2.0 mg/cm2) @ 5.0 MeV/u Ni Pb Angles of detection for projectile/recoil in the T-REX setup Software cut to make “safe” T-REX + Miniball Increasing multi-step probability Front CD (150 mm thick) without barrels Adjustable target CD-distance to optimise angles Rear CD + rear barrels (not used for Coulex)

One-neutron transfer: 69Ni Identification of 5/2+ -> info on N=50 shell gap. Previous experiment fits two states; one “bump” (a) GANIL exp. @ ~30 MeV/u M. Moukaddam. Thesis: Évolution de la structure en couches dans les noyaux de masse moyenne: Recherche de l’orbitale 2d5/2 neutron dans le 69Ni. Strasbourg (2012)

One-neutron transfer: 69Ni Identification of 5/2+ -> info on N=50 shell gap. Previous experiment fits two states; one “bump” New experiment better energy matched for l=2 transfer => large cross-section for 5/2+ state(s). High resolution and efficiency of gamma-ray detection will give precise energy of 5/2+ states(s). (b) Q = 3.58 MeV Q = 2.36 MeV d(66Ni,67Ni)p BCD BBarrel FCD (30 mm) (b) J. Diriken. Thesis: Probing positive-parity states in 67Ni through one-neutron transfer reactions. KU Leuven (2013)

Total p+-g coincidences Beam-time request: 68Ni Beam rate Coulex 300 871 5 25 >4; >0.019 W.u. >17; 0.92 W.u. 68Ni beam – 2.1 x 105 ions/s @ Miniball Primary yield – 1 x 106 ions/mC (estimated) 70Ni beam – 2 x 104 ions/mC @ Miniball (assumed) Primary yield – 2 x 105 ions/mC 68Ni Transfer – 5.0 MeV/u Target (thickness) s (5/2+) [mb] SF (5/2+) Run time CD2 (0.2 mg/cm2) 122 0.6 72 h g-ray efficiency Angular coverage Total p+-g coincidences 4% @ 2.5 MeV ~40% 840 (Si 5/2+i → g.s.) 196Pt (2.0 mg/cm2) @ 4.5 MeV/u; 3 shifts 208Pb (2.0 mg/cm2) @ 4.0 MeV/u; 15 shifts + regular ionisation chamber runs with laser ON/OFF to accurately monitor contamination + beam dump g rays ~50% 70Ga contamination = ~50% Laser OFF runs If 2.7 W.u.; Ig(2+ -> 0 +) = 117 counts per day Or 10 W.u.; Ig(2+ -> 0 +) = 407 counts per day 70Ni 196Pt (2.0 mg/cm2) @ 3.5 MeV/u

+1 shift for setup of each beam Summary Coulomb excitation – 68Ni 68Ni beam @ 4.0, 4.5, 5.0 MeV/u One-neutron transfer – 69Ni 70Ni beam @ 3.5 MeV/u Coulomb excitation – 70Ni 18 shifts 9 shifts 12 shifts +1 shift for setup of each beam 41 shifts

68Ni (Z=28, N=40) b-decay proposal : 100 (constant <E2>) 75 0.11 obtain precise gamma- and electron transition intensities between the 0+ and 2+ states Experiment Calculated transition properties (2+) 2+ 0+ (2+) 2+ 0+ 100 (constant <E2>) 75 0.11 44 1.2 100 Mueller PRC (2000), Flavigny (2013, IS467)

69Ni (Level Scheme)

Beam contamination Ionisation chamber: Mn/Fe (Z=25/26) previously separable(a) Easy to separate Ni/Ga (Z=28/31)… Advantage of direct beam measurement, high statistics quickly = short runs (a) J. Van de Walle, et al., Eur. Phys. J 42, 401-406 (2009).

Integrated cross section : Gs = 3 mb State at 2.5 MeV(d5/2) = 13 mb Proton stopped in dE BCD and Barrel for GS BBarrel used alone for 2.5 MeV states Integrated cross section (Barrel only) : Gs = 3.5 mb State at 2.5 MeV(d5/2) = 54 mb RatioTREX(gs) = 6,5/17 *0,95 ~ 37% RatioTREX(d5/2) = 67/122 *0,95 ~ 47%

d(66Ni,67Ni)p

69Ni: updated motivation N=50 gap size influences energy and strength distribution of 5/2+ states. LNPS shell model calculations with 3 different assumed gaps. ~50/~50 distribution of 2 states at 2.0-2.5 MeV consistent with observation. Precise measurement will constrain calculations. M. Moukaddam. Thesis: Évolution de la structure en couches dans les noyaux de masse moyenne: Recherche de l’orbitale 2d5/2 neutron dans le 69Ni. Strasbourg (2012)

70Ni: updated motivation Y. Tsunoda JPG (2013), arXiv [nucl-th] 1309.5851v1

Previous 68Ni Coulex at ISOLDE B(E2; 0+1 -> 2+1) = 2.8+1.2-1.0 x 102 e2 fm4

Total p+-g coincidences Most recent simulation Transfer – 5.0 MeV/u Scenario Target (thickness) s (5/2+) [mb] SF (5/2+) Run time g-ray efficiency Angular coverage Total p+-g coincidences Current CD2 (0.2 mg/cm2) 122 0.6 72 h 4% @ 2.5 MeV ~40% 840 Worst “ 0.5 3% @ 2.5 MeV 20% 280 Compensate CD2 (1.0 mg/cm2) 1420 Most recent simulation 3.2% @ 2.5 MeV 47% 5370 Eloss ~100 keV Other states? Negative parity states not 1n configuration, hence SF << 1. Cross-section small regardless.

Miniball + TREX: Ge efficiency Energy [keV] Absolute efficiency

Beam rates Nucleus 68Ni (ions/mC) 70Ni (ions/mC) Requested yields 1 x 106 2 x 105 Database values 4 x 105 1 x 104 Recent measurements 8 x 105 N. Bree Coulex ~106