1 / 56

Structure of 68 Ni: new insights on the low-lying 0 + and 2 + s tates from

Structure of 68 Ni: new insights on the low-lying 0 + and 2 + s tates from few-neutron transfer on 66 Ni and β-decay of 68 Co. 40. Piet Van Duppen KU Leuven, Belgium for the ISOLDE IS467, IS469 and IS504 collaborations. 69 Zn. 71 Zn. 72 Zn. 73 Zn. 68 Zn. 70 Zn. 66 Cu.

niles
Download Presentation

Structure of 68 Ni: new insights on the low-lying 0 + and 2 + s tates from

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Structure of 68Ni: new insights on the low-lying 0+ and 2+ states from few-neutron transfer on 66Ni and β-decay of 68Co 40 Piet Van Duppen KU Leuven, Belgium for the ISOLDE IS467, IS469 and IS504 collaborations 69Zn 71Zn 72Zn 73Zn 68Zn 70Zn 66Cu 67Cu 68Cu 69Cu 70Cu 71Cu 72Cu 65Cu Z = 28 65Ni 66Ni 67Ni 69Ni 70Ni 71Ni 78Ni 64Ni g9/2 63Co 64Co 65Co 66Co 67Co 68Co 69Co 70Co N = 40 68Ni p3/2, f5/2, p1/2 d5/2 N = 50

  2. Experimental approach: 3 complementary data sets 3s1/2 2d5/2 1g9/2 28 40 28 50 2p1/2 lx • 66Ni(d,p)67Ni • Single-particle structure (68Ni x n-1) • Spin-parity of excited states • Identification of d5/2 states (across N=50) • IS469 - PhD thesis, J.Diriken 1f5/2 llllll 40 28 2p3/2 llll llllllll llllllll p 1f7/2 n 67Ni

  3. Experimental approach: 3 complementary data sets • 66Ni(t,p)68Ni • Nature of 0+ states in 68Ni • → 2n-2h • IS504 - PhD thesis, J. Elseviers 3s1/2 2d5/2 1g9/2 28 28 40 50 2p1/2 ll • 66Ni(d,p)67Ni • Single-particle structure (68Ni x n-1) • Spin-parity of excited states • Identification of d5/2 states (across N=50) • IS469 - PhD thesis, J.Diriken 1f5/2 llllll 40 28 2p3/2 llll llllllll llllllll p 1f7/2 n F. Recchia et al. PRC80, 041302R (2013) S. Suchyta et al., PRC89 021301R (2013) 68Ni

  4. Experimental approach: 3 complementary data sets • 66Ni(t,p)68Ni • Nature of 0+ states in 68Ni • → 2n-2h • IS504 - PhD thesis, J. Elseviers • b-decay of 68Co  68Ni • Reviseddecayscheme • b-g-E0 coincidences • Exp. B(E2) ratios • IS467 - F. Flavigny 3s1/2 2d5/2 1g9/2 28 28 40 50 2p1/2 ll • 66Ni(d,p)67Ni • Single-particle structure (68Ni x n-1) • Spin-parity of excited states • Identification of d5/2 states (across N=50) • IS469 - PhD thesis, J.Diriken 1f5/2 llllll 40 28 2p3/2 llll llllllll llllllll p 1f7/2 n F. Recchia et al. PRC80, 041302R (2013) S. Suchyta et al., PRC89 021301R (2013) 68Ni

  5. One-neutron transfer reaction: 66Ni(d,p)67Ni

  6. Beam production Resonant Laser Ion Source - Z-selectivity Mass separation - A/Q-selectivity Post-acceleration (REX-ISOLDE) UCxtarget (~ 50 g/cm2) RIB: Q=+1 proton beam (1.4 GeV, ~2 mA) • 66Ni(d,p)67Ni66Ni(t,p)68Ni • - 2.85 MeV/u - 2.6 MeV/u • - 4.0 x 106pps - 2.0 x 106pps • - Beam purity >99% - Beam purity>86% • - 100 mg/cm² CD2 target - 500 mg/cm² 3H loaded Ti target • (40 mg/cm23H) • - Measurement time: 130h - Measurement time:  100h PVD and K. Riisager J.Phys.G: 38 (2011) 024005

  7. 66Ni(d,p)67Ni : Experimental Setup • 8 DE-Erest Barrel det. • 1 DE-Erest CD detectors • 8 Miniball triple (HPGe) clusters • Crystals: 6-fold segmented • 5% efficiency at 1.33 MeV • Proton detection in T-REX: • Identification • Energy • Angular distribution • g detection in Miniball: • Energy • Angular distribution • (Doppler correction) Miniball: Warr EPJ49 (2013) T-REX: Bildstein EPJ48 (2012)

  8. 66Ni(d,p)67Ni (Q=+3.58 MeV) proton - gamma: prompt random no ground state transitions ground state transitions

  9. Relative SFs 9/2+ 1/2- 5/2- 5/2+ 5/2+ 3/2- • Identified d5/2 (and s1/2) single-particle strength at 'low' excitation energy • Comparison with shell model calculations (LNPS int. [1]) and with 88Sr(3He,d)89Y (Z=39, N=50) • d5/2 fragmented but shifted (around 1 MeV) at higher energy [1] S. Lenzi et al., PRC82 054301 (2010)

  10. b-decay of 68Co low-spin isomer to levels in 68Ni

  11. b-decay studies in the 68Ni region using resonant laser ionization • Production of pure 68Mn source at ISOLDE: • p(1.4 GeV) + UCx • Z selection: Laser ionisation (RILIS) • A/Q selection: Spectrometer (HRS) 68Ni 29 s 68Co (7-) T1/2= 0,23(3) s (1+,3+) T1/2 = 1,6(3) s 68Fe 132 ms 68Mn 28 ms laser on laser off 68Fe decay 68Co decay 68Ga decay 136I decay 67Fe decay 67Co decay 2+-0+ - 68Ni [1] W. F. Mueller et al., PRC61 054308 (2000)

  12. Feeding of 0+2 state in 68Ni : b-g-E0 coincidences 68Co (1,3)+ Time difference: tb – tE0 b 1,6(3) s 2+ 2743 g (1139 keV) 0+ 1604 270(5) ns E0 (55% conv. e, 45% pair cr.) 0+ 68Ni Coincidentg rays • b-g-E0 coincidences (590 events) : • 1139 and 2421 keVfeeding0+2 • E(0+2) = 1603,6(6) keV in agreement • 1603,5(3) in [1]. • 1605(3) in [2] • Irel(0+2→0+1) = 19(8) % Top view: beam g b e- [1] F. Recchia et al., PRC88 041302 (2013) [2] S. Suchyta et al., PRC89 021301R (2013)

  13. B(E2) ratios • Exp. VS SM calculations: • 1 – Using the LNPS interaction [1] • 2 – Monte-Carlo shell model calculations [2] Fromexperiment: • Main results: • 2+1 → 0+2 • Irel < 0.7(2) % → R < 17Th: R=12 (MSCM), 4 (LNPS) MCSM [2] 0+1 0+2 2+1 [1] S. Lenzi et al., PRC82 054301 (2010) [2] Y. Tsunoda et al., PRC89 031301R (2014) [3]d(E2/M1)=-1.5+0.9-1.2 from C.J. Chiara et al, PRC86 041304R (2012)

  14. B(E2) ratios • Exp. VS SM calculations: • 1 – Using the LNPS interaction [1] • 2 – Monte-Carlo shell model calculations [2] Fromexperiment: • Main results: • 2+1 → 0+2 • Irel < 0.7(2) % → R < 17Th: R=12 (MSCM), 4 (LNPS) • 0+3 → 2+1 • Th. partial T1/2 of 108 and 1.5 ns (MCSM,LNPS) • Large difference : lifetime measurement needed. 0+3 MCSM [2] 0+1 0+2 2+1 [1] S. Lenzi et al., PRC82 054301 (2010) [2] Y. Tsunoda et al., PRC89 031301R (2014) [3]d(E2/M1)=-1.5+0.9-1.2 from C.J. Chiara et al, PRC86 041304R (2012)

  15. B(E2) ratios • Exp. VS SM calculations: • 1 – Using the LNPS interaction [1] • 2 – Monte-Carlo shell model calculations [2] Fromexperiment: • Main results: • 2+1 → 0+2 • Irel < 0.7(2) % → R < 17Th: R=12 (MSCM), 4 (LNPS) • 0+3 → 2+1 • Th. partial T1/2 of 108 and 1.5 ns (MCSM,LNPS) • Large difference : lifetime measurement needed. • 2+2 → 2+1 • Irel= 11(2)% → R = 448 +185-311 using [3] • R = 29 and 278 (MCSM,LNPS) 0+3 2+2 MCSM [2] 0+1 0+2 2+1 [1] S. Lenzi et al., PRC82 054301 (2010) [2] Y. Tsunoda et al., PRC89 031301R (2014) [3]d(E2/M1)=-1.5+0.9-1.2 from C.J. Chiara et al, PRC86 041304R (2012)

  16. B(E2) ratios • Exp. VS SM calculations: • 1 – Using the LNPS interaction [1] • 2 – Monte-Carlo shell model calculations [2] Fromexperiment: • Main results: • 2+1 → 0+2 • Irel < 0.7(2) % → R < 17Th: R=12 (MSCM), 4 (LNPS) • 0+3 → 2+1 • Th. partial T1/2 of 108 and 1.5 ns (MCSM,LNPS) • Large difference : lifetime measurement needed. • 2+2 → 2+1 • Irel= 11(2)% → R = 448 +185-311 using [3] • R = 29 and 278 (MCSM,LNPS) • 2+3 and 2+4 • Qualitative agreement for (2+4) • Significant discrepancies for (2+3) 2+4 0+3 2+2 4483 keV MCSM [2] 3980 keV 0+1 0+2 2+1 2+3 [1] S. Lenzi et al., PRC82 054301 (2010) [2] Y. Tsunoda et al., PRC89 031301R (2014) [3]d(E2/M1)=-1.5+0.9-1.2 from C.J. Chiara et al, PRC86 041304R (2012)

  17. Two-neutron transfer reaction: 66Ni(t,p)68Ni

  18. 3H(66Ni,p)68Ni : Results - Q = 5.12 MeV Proton - gamma coincidences 815 2847 2743 1139 709 5- 0,86 ms 478 41+ 21+ 1115keV 22+ 01+ 2744keV 21+ 01+ 2033keV Counts / 2keV 2033 270(5) ns Backward CD (153-173°) ground state 68Ni 2743 2+ 0+ 2511 1621(28) keV / 4.8(16) % of gs 2+ 2033 2033(10) keV/ 28(4) % of gs 1604 0+ 21+ 01+ background 0+ 0

  19. Reaction + Structure model 2d5/2 1g9/2 28 Two-neutron transfer : Direct + Sequential 2p1/2 ll 1f5/2 llllll llll 2p3/2 llllllll llllllll p 1f7/2 n 67Ni 66Ni 68Ni • Parameters of ourcalculations: • Finite-range DWBA (code FRESCO[1] ) • Glob. Pot. : 3H+66Ni and 1H+68Ni • Twonucleonoverlap amplitudes (TNA’s) • Code: NUSHELL (A. Brown, MSU) [2] • Interaction jj44pna from [3] • Model space: f5/2,p3/2,p1/2,g9/2 • Calculated68Ni energies • E(0+2) = 1593 kev, E(2+1) = 2077 keV 28 40 50 40 28 [1] www.fresco.org.uk [2] B. A. Brown and W. D. M. Rae, Nushell@MSU 2007 [3] A. F. Lisetskiy et al., PRC 70, 044314 (2004)

  20. Reaction + Structure model 2d5/2 1g9/2 28 Two-neutron transfer : Direct + Sequential 2p1/2 ll 1f5/2 llllll llll 2p3/2 llllllll llllllll p 1f7/2 n 67Ni Neutron occupation numbers Proton occupation numbers 66Ni 68Ni jj44pna A3DA (MCSM) LNPS 68Ni • Parameters of ourcalculations: • Finite-range DWBA (code FRESCO[1] ) • Glob. Pot. : 3H+66Ni and 1H+68Ni • Twonucleonoverlap amplitudes (TNA’s) • Code: NUSHELL (A. Brown, MSU) [2] • Interaction jj44pna from [3] • Model space: f5/2,p3/2,p1/2,g9/2 • Calculated68Ni energies • E(0+2) = 1593 kev, E(2+1) = 2077 keV ) 40 28 50 Averagenumber of neutrons in a given state: 40 28 [1] www.fresco.org.uk [2] B. A. Brown and W. D. M. Rae, Nushell@MSU 2007 [3] A. F. Lisetskiy et al., PRC 70, 044314 (2004)

  21. 66Ni(3H,p)68Ni : Angular distributions • Conclusions: • Reasonable agreement th/exp for 0+1,2 states • Th: s(0+2) / s(0+1) in [3 ; 7 ] % • Exp: s(0+2) / s(0+1) = 4.8(16) % •  Validation of structure input 0+1 Small CM angles 0+2 • Experiment consistent with 0+2 in 68Ni being a neutron excitation above N=40

  22. Outlook • Structure of (the region around) 68Ni (Z=28, N=40) studied through b-decay and one and two-neutron transfer reactions • Strength of the neutron d5/2 lower compared to shell-model calculations • Character of the 0+2 state compatible with neutron excitations across N=40 • Future experiments at HIE-ISOLDE in the region of 68Ni: • 80Zn(d,p)81Zn, [R. Orlandiet al., INTC-2012-051 P-352] • 70Ni(d,p)71Ni, [J.J ValienteDobonet al., INTC-2012-050 P-351] • 68Ni(d,p)69Ni,[accepted] • d5/2 single particle strength above N=50 • Coulomb excitation of 68Ni, 70Ni • Absolute B(E2) values • Decay of 68Mn with the new ISOLDE Decay Station[accepted] • Lifetime of 0+3→2+1 transition (478 keV)

  23. Detector array: TREX and MINIBALL • proton detection in T-REX: • identification • energy • angular distribution • gamma detection in Miniball: • energy • angular distribution (Doppler correction) Miniball clusters • 8 DE-Erest barrel detectors • 1 DE-Erest CD detectors • Covered lab range: 28° to 78° ° (Forw. Barrel) • 102 to 152° (Back. Barrel) • 152 to 172° (Back. CD) • 8 Miniball triple (HPGe) clusters • Each crystal: 6-fold segmented • 5% efficiency at 1.33 MeV Miniball: Warr EPJ49 (2013) T-REX: Bildstein EPJ48 (2012)

  24. DWBA calculation using FRESCO • Normalization elastically scattered deuterons • Global Optical Model Potential's • (Han PRC74, 044615 (2006)). I(66Ni) = 4.1(3) 106pps • Outgoing channel: • (Koning and Delaroche NPA713, 231 (2003).). • Different optical potentials checked: angular distribution doesn't change substantially, variation on differential cross sections (and rel. SF) up to 10%

  25. ANi(d(10 MeV),p)A+1Ni (Schiffer PRL108 (2012), PRC87 (2013) ) 2H(66Ni(2.85 MeV/u),p)67Ni Combined one-neutron stripping and pick-up p1/2 (s1/2) g9/2 1 Rel. SF to g9/2 f5/2 d5/2 p3/2 • 25 to 30 % uncertainty on rel. SF

  26. Comparison with a particle-core coupling model 2H(66Ni(2.85 MeV/u),p)67Ni 1724 p1/2 (s1/2) g9/2 Part.-core coupled to 68Ni calculation 1 Rel. SF to g9/2 f5/2 d5/2 p3/2 Orosand Mantica NPA 669 (2000)

  27. 3H(66Ni,p)68Ni : Backward CD Backward CD (153-173°) 815 2847 2743 1139 709 5- 0,86 ms (t,p) Eex= 0 MeV 478 2033 270(5) ns (t,p) Eex= 6 MeV 68Ni • CD data only (before beam tuning) • Population of 02+ and 2+1states (relative to gs) • E = 1621(28) keV - 4.8(16) % of gs • E = 2033(10) keV - 29(3) % of gs • Non-observed direct population of 03+ , 22+ and 2+3states • 0+3 (2512 keV) < 2% based on 478 keV transition • 2+2 (2744 keV) < 4% based on 709 keV transition • 2+3 (4026 keV) < 3% based on 1515 keV transition 2743 2+ 0+ 2511 2033 2+ 1604 0+ 0+ 0

  28. Calculated occupations Neutron occupation numbers Averagenumber of neutrons in a given state Interaction: jj44pna [1] Model space: f5/2,p3/2,p1/2,g9/2 2d5/2 1g9/2 28 40 50 28 2p1/2 ll Proton occupation numbers 1f5/2 llllll 28 40 2p3/2 llll llllllll llllllll p 1f7/2 n [1] A. F. Lisetskiy et al., PRC 70, 044314 (2004) [2] S. Lenzi et al., PRC82 054301 (2010) [3] Y. Tsunoda et al., PRC89 031301R (2014)

  29. 66Ni(3H,p)68Ni : Angular distributions Direct transferonly Ground state (0+1) Transfer to gsdominated by (p)2 configurations Content of wfwith g9/2empty: 42% 0+2 state (1605 keV) Transfer to 0+2dominated by (g9/2)2 configurations Content of wfwith g9/2empty: 14%

  30. 66Ni(3H,p)68Ni : Angular distributions Direct transferonly Direct + sequential Ground state (0+1) 0+2 state (1605 keV) Significant effect of sequential transfer  Shape changes

  31. 66Ni(3H,p)68Ni : Angular distributions • Conclusions: • First calculation far toolow • Work in progress • Phase conventions are crucial Preliminary Calculationfrom G. Potel [1]

  32. B(E2) ratios S. Suchyta et al., PRC89 021301R (2014) [1] S. Lenzi et al., PRC82 054301 (2010) [2] Y. Tsunoda et al., PRC89 031301R (2014) [3] S. Suchyta et al., PRC89 021301R (2014)

  33. Particle identification DE [keV] Etot [keV] Tritons: Elastic scattering Deuterons: (t,d) 3H(66Ni,67Ni)2H Protons: Elastic + (t,p) 3H(66Ni,68Ni)1H

  34. 3H(66Ni,p)68Ni : Excitation energy Backwarddirection (90°-180°) Forwarddirection (0°-90°) • Most of the feeding to statesbetween 5-8 MeV • E = 1621(28) keV - 5.4(11) % of gs • Direct population of 21+ state at 2033 keV • 29(2)% relative to ground state (see next slide) • No direct population of 2+2 at 2743 keV

  35. One and two-nucleon amplitudes Courtesy of A.Brown, Bertschfest (2012)

  36. NUSHELL calculations -TNA’s

  37. 67Ni Elasticallyscatteredprotons Excitation Energy Spectrum Colors: feeding to all different levelspopulated in 67Ni

  38. Constructing the level scheme: spin/parity

  39. Constructing the level scheme 67Ni Condition: prompt proton-gMBcoincidence Resulting information: 67Ni excitation energyfrom proton kinematics

  40. Improved Level scheme for 67Ni Identification of 5/2+ states (neutron excitationsabove the N=50 shell gap, d5/2 )

  41. b-decay studies in the 68Ni region using resonant laser ionization • Pure Mn sources • Z selection: Laser ionisation (RILIS) • A/Q selection: Spectrometer (HRS) • A=68 • LISOL: 2 isomers in 68Co • (7-) T1/2= 0,23(3) s • (1+,3+) T1/2 = 1,6(3) s • ISOLDE: Selectivity of 68Fegs (0+) decay 58Mn 3.0(1)s

  42. Decay scheme • New: • 710 keV intensity • 1139 and 2421 keV placement • 694 keV from b-delayed n-em. • 814 keV intensity –5- isomer • Irel(0+2→0+1 = 19(8) % • Upper limits: • Irel(0+3→0+2) < 2(1)% • Irel(0+3→0+2) • Irel(0+3→0+1) <4(1)% [1] W. F. Mueller et al., PRC61 054308 (2000)

  43. Decay chain A=68 • Intensity balance: test of completeness • Determination of missed feeding: • Direct b feeding of gs • Direct b-del.n feeding to gs or isomeric state • Missed E0 decay • Missed g ray feeding to gs or isomeric states • Method: • Ndecays (68Mn) from detected b particles • corrected for laser off (68Ga) • corrected for subsequent decays in time window • b detection efficiency • Ndecays (68Mn) from detected g rays in 68Fe • Strongest gs branch corrected for other gs decays • Include Pn branch • g detection efficiency 34.3(10) ms 0.42(3) s Missed feeding: 35(7)% 189(6) ms 67Co 0.33(3) s 1.6(3) s 21(1) s Missed feeding: 42(10)% [1] W. F. Mueller et al., PRC61 054308 (2000) [2] S. N. Liddick et al., PRC85 014328 (2012)

More Related