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N=28, Shell Closure and Shapes

N=28, Shell Closure and Shapes. L. Gaudefroy CEA/DIF – Bruyères-le-Châtel. Courtesy of M. Rejmund. LIA – EFES Workshop – GANIL : 2-4 March 2009. N=28. f 5/2. p 1/2. p 3/2. f 7/2. d 3/2. s 1/2. Empty. Full. p (s 1/2 & d 3/2 ). d 5/2. Ar. Ca. Si. S. N=28. Shell Structure.

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N=28, Shell Closure and Shapes

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  1. N=28, Shell Closure and Shapes L. Gaudefroy CEA/DIF – Bruyères-le-Châtel Courtesy of M. Rejmund LIA – EFES Workshop – GANIL : 2-4 March 2009

  2. N=28 f5/2 p1/2 p3/2 f7/2 d3/2 s1/2 Empty Full p(s1/2 & d3/2) d5/2 Ar Ca Si S N=28 Shell Structure Experimental difficulty d3/2 p3/2 p3/2 p3/2 s1/2 s1/2 28 f7/2 d5/2 f7/2 d5/2 f7/2 d5/2 p n p p n n 46Ar 42Si 44S 28 28 20 40 14 20 14 28 8 16 • 1st magic number originating from SO interaction • -Evolution of SO with isospin • -Role of pn interaction on structure fp Without SO interaction sd

  3. N=28 Shell Model Mean Field F. Nowacki and A. Poves, PRC 79, 014310 (2009) S. Péru et al. EPJA 9, 35 (2000) Agreement on the reduction of N=28 in exotic nuclei

  4. N=28 -E(2+) = 1577 keV H. Scheit et al. PRL 77, 3967 (1996) -E(2+) = 1297 keV T. Glasmacher et al. PLB 395, 163 (1997) -E(2+) = 1330 keV S. Grévy et al. EPJ A 25 (2005) -E(2+) = 770 keV B. Bastin, S. Grévy et al. PRL 99 (2007) 2+ 0+ : 770 ± 20 keV NEW Progressive decrease of E(2+1) at N=28

  5. In this talk Empty Full p(s1/2 & d3/2) Ar Ca Si S Def. Spher. Part I : +Transfer reactions at Z=18 -46Ar28(d,p) & 44Ar26(d,p) Part II : +Magnetic moment at Z=16 -Study of 43mS27.

  6. (d,p) reaction : Principle p d d MUST 8 modules Si 960 strips X-Y qp,Ep qp, Ep SPEG Spectro. Exotic beam 46Ar @ 10 MeV.A Ep CATS Beam tracking SPIRAL/GANIL CD2 47Ar 46Ar qp Study of the fp single particle states at N=28 (d,p) transfer reaction f5/2 p1/2 p3/2 28 f7/2 46Ar28 47Ar29

  7. 46Ar(d,p)47Ar : Résults GS ℓ=1 ℓ=3+4 1.13 5.50 3.33 ℓ=4 3.98 2.65 1.74 ℓ=3 • New Mass excess for 47Ar • Dm(47Ar)=-25.20(8)MeV • before :-25.9(1)MeV • Sn = 3.55(8) MeV Before : 4.3 MeV Unknown Spectroscopy

  8. Results: 46Ar 5/2- 5/2- 7/2- 1.6 2+ 1/2- 1.7 0.17 GS 3/2- 47Ar • 1.36 neutrons p3/2 f5/2 p1/2 • 6.64 neutrons f7/2 p3/2 d3/2 s1/2 d5/2 p n 46Ar: 0+ 3.3 0.43 2.7 0.22 46Ar: N=28 eroded => Correlations in the GS of 46Ar 1.1 0.81 GS 0+ 0.61 46Ar f7/2 d3/2 gs s1/2 d5/2 p n Shell Structure L. Gaudefroy, O. Sorlin et al., PRL 97, 092501 (2006)

  9. 44Ar(d,p)45Ar : Results 600 400 200 0 E (MeV) 5

  10. 47Ca27 & 45Ar27 : Shell Model 3/2 3.90 2020 1 1 4 4 0 0 3 3 2 2 20 d3/2 Expt. s1/2 14 d5/2 7/2 3/2 1.08 2.10 0 1420 p np3/2 2+ x nf7/2 47Ca27 3/2 0.76 550 7/2 1.52 0 45Ar27 Expt. ANTOINE code: E. Caurier & F. Nowacki - Strasbourg

  11. N=27 isotones E = ESPE + EMono+EMulti Correl HF-MF Orbits EMulti (MeV) Z Ca 2 1 1 4 4 0 0 3 3 2 2 Ar 9 S 12 3 2 1 E(3/2)-E(7/2) [MeV] 0 -1 -2 Ca S Ar 43S: 3/2 – 7/2 Inversion suggested in F. Sarazin et al. PRL 84, 5062 (2000) L. Gaudefroy et al., PRC 78, 034307 (2007)

  12. g-factor measurement in 43S 488ns (7/2-) 320 (3/2-) 43S -Mass measurement at GANIL: F. Sarazin et al. PRL 84, 5062 (2000) => Low lying isomeric state SM-based interpretation g factor of the isomeric state : -Direct determination of spin/parity. -Test the wave function.

  13. Principle H = - µ B H = g.I B R(t) = A cos(wt+f) w = -gB B I(t) R(t) G - B G + B t t Fragmentation : ~300 43S/sec LISE@GANIL

  14. Results Exp gs Schmidt gSchmidt = ± 2ℓ+1 f7/2 -0.546 (j=ℓ ±1/2) -0.317 p3/2 -1.275 gs=-3.826

  15. Experiment vs. Theories Part. Rotor Particule.+Rotor -K=1/2 decoupled band. GS deformed band: b=+0.30 7/2- (isom.) not in this band Rather spherical Code ANTOINE : Caurier & Nowacki - Strasbourg

  16. Experiment vs. Theories Mean Field : -HFB – Gogny D1S -Blocking -GCM + GOA Ground State: -K=1/2 (from p3/2) -b=0.37 -Decoupling parameter & Inertia parameter=> in agreement with PR States from f7/2 orbit: -Within 400keV -Around b=0 L. Gaudefroy, J.M. Daugas et al, PRL 102,092501 (2009)

  17. Conclusion Part I : 44Ar(d,p), 46Ar(d,p) -Correlations present in the N=28 nucleus 46Ar. -SM description of N=27 isotones showing the evolution of multipolar energy. Part II : g-factor of 43mS -Direct evidence of the inversion of the 7/2- - 3/2- states -Successfully interpreted with 3 models -Deformed ground state K=1/2 band -Rather spherical isomeric state

  18. Collaboration France : CEA-Bruyères-le-châtel, IPNO, GANIL, CEA-Saclay, CSNSM, CENBG, IReS, LPSC Bulgaria : Faculty of Physics Germany : Universität Mainz Hungary : INR Israel : Weizmann Institute Japan : Riken USA : FSU Russia : FLNR/JINR

  19. 44Ar(d,p)45Ar : Exp. vs Theorie 3/2 3.90 2020 2+ x 7/2- 7/2 2.10 0 47Ca27 Code ANTOINE : E. Caurier & F. Nowacki Interaction sdpf: S. Nummela et al. PRC63 (2001) 45Ar27 Satisfactory agreement

  20. More exotic N=27 isotones E = ESPE + EMono + EMulti Correl HF-MF Orbits EMulti (MeV) Z Ca 2 Ar 9 S 12 Si 15 L. Gaudefroy et al. PRC 78, 034307 (2007)

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