1. Structure of N~40 Ni isotopes studied by knock-out reactions Francesco Recchia UNIVERSITÀ DEGLI STUDI DI PADOVA

2. Francesco Recchia – ISOLDE seminar – CERN Overview  Scientific motivation  Study of Ni isotopes: Neutron knock-out with GRETINA and S800 at NSCL  New data on 68 Ni and implications for the structure of its low-spin states 2

3. Francesco Recchia – ISOLDE seminar – CERN f 7/2 d 3/2 d 5/2 p 1/2 1d 1f s 1/2 2s 2p p 3/2 f 5/2 L.S H.O L2L2 N=2 N=3 1g N=4 2d + + d 5/2 1p N=1 p 3/2 p 1/2 g 9/2 The “spin-orbit” magic numbers 3 8 20 28 40 50 40 20 8

4. Francesco Recchia – ISOLDE seminar – CERN 4 H. Grawe, EPJ A 25 (2005) 357 Shell evolution  Disappearance / appearance of magic numbers  P-N attraction between spin-flip partner orbits T. Otsuka et al. EPJ A 20 (2003) 69-73, PRL 95, 232502 (2005), J.D.Holt et al 2012 J. Phys. G: Nucl. Part. Phys. 39 085111  Monopole part of the tensor term  Monopole part of the three-body force m m m’  T. Otsuka Phys. Scr. T152 (2013) 014007

5. Francesco Recchia – ISOLDE seminar – CERN The effective interaction A multipole expansion monopole Multipole - represents a spherical mean field extracted from the interacting shell model - determines the single particle energies or ESPE. - represents a spherical mean field extracted from the interacting shell model - determines the single particle energies or ESPE. - correlations - energy gains - correlations - energy gains Deformation 5 Interplay spectacular phenomena ioi

6. Francesco Recchia – ISOLDE seminar – CERN The islands of inversion (N=8,20,28) At N=8 and N=20 the h.o. shell gap vanishes for very neutron rich nuclei. Island of inversion T. Otsuka EPJ S. Top. 156, 169 (2008) 42 Si Deformed intruder configurations fall below the spherical ones A. Poves, 2011 N=8 N=20 N=28 Si 6 11Li

7. Francesco Recchia – ISOLDE seminar – CERN Islands of inversion 32 Mg 20 sd p 3/2 f 7/2 20 64 Cr 40 pf d 5/2 g 9/2 40 12 Be 8 p d 5/2 s 1/2 8 N=1 N=2 N=3 N=4 Islands of Inversion are observed at the harmonic oscillator magic numbers. 7

8. Francesco Recchia – ISOLDE seminar – CERN 8 68 Ni region

9. Francesco Recchia – ISOLDE seminar – CERN Observables at N=40 E(2 + ) B(E2) 9 R.Broda et al., PRL 74, 868 (95) O. Sorlin et al. PRL 88, 092501 (2002) W. Rother et al. Phys.Rev.Lett. 106, 022502 (2011) A. Kankainen, et al., J.Phys.G 39, 093101 (2012)

10. Francesco Recchia – ISOLDE seminar – CERN Neutron excess and shell migration  f 7/2 p 3/2 f 5/2 p 1/2 g 9/2 40 32 protons neutrons protons 0f 7/2 1p 3/2 1p 1/2 0f 5/2 0g 9/2 neutrons Z = 28 40 28 0f 7/2 1p 3/2 1p 1/2 0f 5/2 0g 9/2 neutrons 0f 7/2 protons 32 Z = 20 Monopole shifts 10 68 Ni is at the limit of region of deformation

11. Francesco Recchia – ISOLDE seminar – CERN 68 Ni low spin states  Collective structure in 68 Ni?  Based on deformed excited states? 11  f 7/2 p 3/2 f 5/2 p 1/2 g 9/2 40 32 protons neutrons  f 5/2 28 YES: Type II shell evolution Y.Tsunoda, T.Otsuka et al. arXiv [nucl-th]23/9/2013

12. Francesco Recchia – ISOLDE seminar – CERN 12 Single Particle Strength in the odd, neutron-rich Ni isotopes  Persistence of customary magic numbers  Spin-isospin part of the nn interaction  Single particle strength in A-1 Ni components in the g.s. in A Ni comparison to shell model calculations  Provide the first gating transitions for GS data

13. Francesco Recchia – ISOLDE seminar – CERN Example: 82 Se → 72 Ni K500 K1200 A1900 production target ion sources coupling line stripping foil wedge focal plane  p/p = 1% 82 Se 13+, 12 MeV/u 82 Se 34+, 140 MeV/u 82 Se fragment yield after targetfragment yield after wedgefragment yield at focal plane 72 Ni 13 Figure courtesy A. Stolz

14. Francesco Recchia – ISOLDE seminar – CERN A1900 fragment separator Reaction product identification S800 spectrograph 14 69Cu 68Ni 67Co TOF obj TOF xfp Reaction target 100-281mg/cm 2

15. Francesco Recchia – ISOLDE seminar – CERN A1900 fragment separator Reaction product identification S800 spectrograph 15 Reaction target 100-281mg/cm 2 73Cu 75Zn 72Ni 74Cu

16. Francesco Recchia – ISOLDE seminar – CERN A1900 fragment separator Reaction product identification S800 spectrograph 16 Reaction target 100-281mg/cm 2 67 Ni* γ β ̴ 0.4c 67 Ni to focal plane S800 68 Ni γ 9 Be

17. Francesco Recchia – ISOLDE seminar – CERN A1900 fragment separator Reaction target 100-281mg/cm 2 Reaction product identification S800 spectrograph 17 67Ni 65Co 66Ni Gated on 68 Ni Velocity vector

18. Francesco Recchia – ISOLDE seminar – CERN A1900 fragment separator Reaction target 100-281mg/cm 2 Reaction product identification S800 spectrograph 18 K. Meierbachtol et al. NIM A 652 (2011) 668–670

19. Francesco Recchia – ISOLDE seminar – CERN 68 Ni is produced from 70 Ni A surprise in 68 Ni… 19

20. Francesco Recchia – ISOLDE seminar – CERN Low-spin states in 68 Ni 20 1770(30) 0+0+ Bacchus@IPN Orsay GIROD et al. 1988

21. Francesco Recchia – ISOLDE seminar – CERN Low-spin states in 68 Ni 21 1770(30) 0+0+ Lisol@KU Leuven Mueller et al. 2000

22. Francesco Recchia – ISOLDE seminar – CERN Low-spin states in 68 Ni 22 1770(30) 0+0+ Pauwels et al. 2012 Predicted a new 0 + level at 2202 keV N=40Z=40

23. Francesco Recchia – ISOLDE seminar – CERN Low-spin states in 68 Ni 23 1770(30) 0+0+ 2202 0+0+ EXOGAM-VAMOS@GANIL Dijon et al. 2012  2p2h

24. Francesco Recchia – ISOLDE seminar – CERN Low-spin states in 68 Ni 24 1770(30) 0+0+ 2202 0+0+ EXOGAM-VAMOS@GANIL Dijon et al. 2012 GAMMASPHERE@ANL Chiara et al. 2012  2p2h

25. Francesco Recchia – ISOLDE seminar – CERN A1900 fragment separator Reaction target 100-281mg/cm 2 Reaction product identification S800 spectrograph 25 K. Meierbachtol et al. NIM A 652 (2011) 668–670 70 Ni → 68 Ni Clean P-D coincidences

26. Francesco Recchia – ISOLDE seminar – CERN A surprise in 68 Ni !!  in the hodoscope prompt 26

27. Francesco Recchia – ISOLDE seminar – CERN Lifetime ch 350(50) ns 27

28. Francesco Recchia – ISOLDE seminar – CERN GIROD PRC 1988 28

29. Francesco Recchia – ISOLDE seminar – CERN 2nKO with GRETINA at NSCL… (a) CsI(Na) spectrum, 68 Ni-gated; (b) GRETINA spectrum, gate on 511 and 68 Ni 29

30. Francesco Recchia – ISOLDE seminar – CERN DIS experiment  440-MeV 70 Zn + 208 Pb DIS reaction at ATLAS  Stand-alone Gammasphere (100 Ge detectors) Thick target stops all reaction products Beam period 412 ns Trigger on  fold ≥3 DIS produces cross- coincident partner nuclei 30 Analysis by CJ Chiara – University of Maryland/ANL

31. Francesco Recchia – ISOLDE seminar – CERN  Time following an RF pulse 50 ns 412 ns Prompt : t(  ) in region 1 Delayed : t(  ) in region 2 or 3 Coincidence cubes: PPP – all three  ’s are prompt PPD – two prompt, one delayed PDD – one prompt, two delayed and within 50 ns of each other DDD – all three  ’s are delayed 1 in 5 beam pulses allowed to hit the target Prompt  rays – emitted by excited states directly populated in the reaction Delayed  rays – emitted by isomeric states or in the  decay of the reaction products Ge timing 31 Analysis by CJ Chiara – University of Maryland/ANL

32. Francesco Recchia – ISOLDE seminar – CERN DIS with Gammasphere at ATLAS… (delayed Po lines) (a,b) gate 662/Po; (c) gate 662/1139 32 Analysis by CJ Chiara – University of Maryland/ANL

33. Francesco Recchia – ISOLDE seminar – CERN Measured branching ratios  relative B(E2)’s for decays to 0 + 1,2 and 2 + 1 states. * * W. F. Mueller et al., PRC 61, 054308 (2000) 33

34. Francesco Recchia – ISOLDE seminar – CERN B(E2) ratios, normalized at each level 2 + 2 decay favors 2 + 1 (mixed) SM calcs with 56 Ni core + f 5/2 pg 9/2 Generally good energies Small ‘tweak’  B(E2) ratios from 2 + 2 agree(0.4%) (g 9/2 ) m components...; 0 + 3 no good m=2 (68%) m=4 (29%) m=0 (42%) m=2 (43%) m=2 (56%) m=4 (28%) 34 g 9/2 p 1/2 28 f 5/2 p 3/2 50 40

35. Francesco Recchia – ISOLDE seminar – CERN B(E2) ratios, normalized at each level 2 + 2 decay favors 2 + 1 (mixed)  fp + f 5/2 pg 9/2 d 5/2 0 + 3 is  excitation B(E2)’s reproduced B(E2)2 + 1 →0 + 2 is 16 times B(E2)2 + 2 →0 + 2 35 g 9/2 p 1/2 28 f 5/2 p 3/2 50 40 p 1/2 28 f 5/2 p 3/2 40 d 5/2 f 7/2 

36. Francesco Recchia – ISOLDE seminar – CERN N. Shimuzu, T. Otsuka et al. Prog. Theor. Exp. Phys. (2012) 01A205 36 MC Shell Model

37. Francesco Recchia – ISOLDE seminar – CERN MC Shell Model Tsunoda JPG (2013), [nucl-th] 1309.5851v1 (2013) 37 N. Shimuzu, T. Otsuka et al. Prog. Theor. Exp. Phys. (2012) 01A205

38. Francesco Recchia – ISOLDE seminar – CERN Conclusions  68 Ni studied via 2nKO with GRETINA at NSCL and via DIS with Gammasphere at ATLAS  Energy of 0 + 2 isomer firmly established  Mixing of configurations for low-lying states supports picture of shape coexistence  What comes next?  68 Ni:  Absolute lifetimes / B(E2)’s needed!  Study of the branchings with larger statistics  2 proton transfer cross sections  More 2 + levels  Heavier Ni isotopes 38

39. Francesco Recchia – ISOLDE seminar – CERN Thank you! Experiment: C. J. Chiara, R. V. F. Janssens, D. Weisshaar, A. Gade, W. B. Walters, M. Albers, M. Alcorta, V. M. Bader, T. Baugher, D. Bazin, J. S. Berryman, P. F. Bertone, B. A. Brown, C. M. Campbell, M. P. Carpenter, J. Chen, H. L. Crawford, H. M. David, D. T. Doherty, C. R. Hoffman, F. G. Kondev, A. Korichi, C. Langer, N. Larson, T. Lauritsen, S. N. Liddick, E. Lunderberg, A. O. Macchiavelli, S. Noji, C. Prokop, A. M. Rogers, D. Seweryniak, S. R. Stroberg, S. Suchyta, S. Williams, K. Wimmer, S. Zhu Theory: B.A.Brown 39

40. Francesco Recchia – ISOLDE seminar – CERN 40

41. Francesco Recchia – ISOLDE seminar – CERN Available online 2 weeks ago!

42. Francesco Recchia – ISOLDE seminar – CERN GRETINA Experiments at NSCL Nuclear Shell Evolution N=Z Mirror Spectroscopy Structure in 221,223 Rn 50-52 Ca neutron knock-out Neutron-rich Ti Odd neutron-rich Ni 34 Si Bubble nucleus? Neutron-rich Si GRETINA commissioning Neutron-rich N=40 nuclei Normal and intruder configurations in the Island of Inversion Nuclear Astrophysics Excitation energies in 58 Zn Measurement of the 56 Ni(d,n) 57 Cu transfer reaction Collective Nuclear Structure Transition matrix elements in 70,72 Ni Quadrupole collectivity in light Sn γ-γ spectroscopy in neutron-rich Mg Neutron-rich C lifetime measurement Collectivity at N=Z via RDM lifetime measurements B(E2:2 → 0) in 12 Be 71-74 Ni excited-state lifetimes Inelastic excitations beyond 48 Ca Triple configuration coexistence in 44 S GT strength distributions in 45 Sc and 46 Ti Search for isovector giant monopole resonance 23 Expts 3360 hrs done through February 2013 Prepared by H. Crawford, LBNL

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44. Francesco Recchia – ISOLDE seminar – CERN The new interaction in the fpgd space LNPS interaction : renormalized realistic interaction + monopole corrections 48 Ca core protons: full pf shell neutrons: p 3/2,f 5/2, p 1/2, g 9/2, d 5/2 40 28 f 7/2 p 3/2 p 1/2 f 5/2 g 9/2 d 5/2 48 Ca  KB3gr for the pf-shell;  monopole corrections to reproduce the Z=28 and N=50 gaps in 78 Ni based on data of neighboring nuclei  KB3gr for the pf-shell;  monopole corrections to reproduce the Z=28 and N=50 gaps in 78 Ni based on data of neighboring nuclei S. M. Lenzi, F. Nowacki, A. Poves, and K. Sieja, PRC 82, 054301 (2010)

45. Francesco Recchia – ISOLDE seminar – CERN The N=40 isotones E (2 + ) B(E2;2 +  0 + ) A change of structure is observed along the isotonic chain in good agreement with the available data Occupation of intruder orbitals and percentage of p-h configurations S.M. Lenzi, F. Nowacki, A. Poves and K. Sieja, PRC 82, 054301 (2010) 45

46. Francesco Recchia – ISOLDE seminar – CERN The energy levels at N=40 cannot be described within the fp or fpg space 420 1131 Neutron-rich Cr and Fe isotopes results and shell-model calculations results and shell-model calculations S. Lenzi, F. Nowacki, A. Poves and K. Sieja 2010 f 7/2 p 3/2 f 5/2 p 1/2 48 Ca g 9/2 d 5/2 68 Ni π ν 46

47. Francesco Recchia – ISOLDE seminar – CERN Cr-Fe-Ni isotopes E (2 + ) B(E2) β~0.35 β~0.3 Fe Cr Ni S.M. Lenzi, F. Nowacki, A. Poves and K. Sieja, PRC 82, 054301 (2010) 47

48. Francesco Recchia – ISOLDE seminar – CERN