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Study of isomeric states using gamma spectroscopy around N=40 C. Petrone 1,2, J. M. Daugas 3, M. Stanoiu 1, F. Negoita 1, G. Simpson 4, C. Borcea 1, R.

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Presentation on theme: "Study of isomeric states using gamma spectroscopy around N=40 C. Petrone 1,2, J. M. Daugas 3, M. Stanoiu 1, F. Negoita 1, G. Simpson 4, C. Borcea 1, R."— Presentation transcript:

1 Study of isomeric states using gamma spectroscopy around N=40 C. Petrone 1,2, J. M. Daugas 3, M. Stanoiu 1, F. Negoita 1, G. Simpson 4, C. Borcea 1, R. Borcea 1, L. Caceres 5, S. Calinescu 1, R.Chevrier 3, L. Gaudefroy 3, G. Georgiev 6, G. Gey 4, C. Plaisir 3, F. Rotaru 1, O. Sorlin 5, J. C. Thomas 5 1 Horia Hulubei National Institute for Physics and Nuclear Engineering, P.O. Box MG-6, 077125 Bucharest- Magurele, Romania 2 Faculty of Physics, University of Bucharest - P.O. Box MG 11, RO 77125, Bucharest-Magurele, Romania, EU 3 CEA, DAM, DIF, F-91297 Arpajon, France 4 ILL, 38042 Grenoble Cedex, France 5 Grand Accélérateur National d’Ions Lours (GANIL), CEA/DSM-CNRS/IN2P3, Caen, France 6 CSNSM, CNRS/IN2P3, 91405 Orsay-Campus, France 1 Carpathian Summer School of Physics Sinaia 2012 cristina.petrone@tandem.nipne.ro

2 Motivation:Neutron-rich nuclei around N = 40 Nuclear structure informations far from stability N = 40 subshell closure for Ni R.Broda et al., Phys.Rev.Lett. 74 (1995) Deformation in 66 Fe  vanishing Isomeric state in 67 Fe M.Sawicka et al., Phys.Rev.C 77,054306(2008)  Nuclear structure of neutron-rich nuclei lying between 68 Ni and 78 Ni-> modelization of astrophysical processes 2 67 Fe

3 role of the g 9/2 for 40 < N < 50 The key role of the g 9/2 for 40 < N < 50 f 7/2 f 5/2 p 3/2 g 9/2 28 40 50  75 Cu  Neutron-rich Cu isotopes (Z=29): 1  outside Z=28 core interacting with g 9/2  Spin-isospin interaction  Tensor force N = 46 ( 75 Cu):  f 5/2 g.s. configuration K.Flanagan, Phys. Rev.C80(2009) J.-M. Daugas Phys.Rev.C 81 (2010)  86 Kr on Ni target 2 isomeric states 1|2 - 1096 1|2 - 454 1|2 - 135 1|2 - 3

4 Experimental set-up 70° Fragments Electron detector (SILI) Shield Veto (Si) HI-detectors(Si) LEPS HPGe Fragments separated in flight using LISE2000 A, Z identification by Energy-loss and TOF informations  Si position sensitive detectors Fragmentation of 86 Kr @ 60 MeV/u on Be (500um) Beam intensity: 4  Ae Implantation foil (Kapton) 75 um  Effective thickness = 219 um Veto detector: Double Side Strip Si detector Al degrador 4 Compact reaction chamber -> high efficiency detection

5 Identification matrix 5 78 Ga 31+ 75 Cu 29+ + 72 Cu 28+ Z AoQ  ΔE, ToF, Bρ  Delayed γ-ray correlations

6 75 Cu gamma spectrum E(keV) J.M.Daugas et al., Phys.Rev.C 81(2010) 66.5(4)keV62.2(4)keV T(ns) 66.5keV transition 62.2keV transition 6 Energy[keV]Number of counts Nb. of counts corr. by eff 62.2(4)keV2483(46)26989(143) 66.5(4)keV2220(47)23053(122)

7 γ-γ coincidences E(keV) 72 Cu decay scheme M.Stanoiu PhD thesis (2003) Coincidence spectra background gated Coincidence spectra 62.2keV gated 270(1.76us) 220 138 51 82 138 6-6- 4-4- 3-3- 2-2- Coincidence spectra 66.5keV gated 7

8 Gamma times Fit function: convolution between a gaussian and an exponential T(ns) Almost 100%feeding from the uppper isomeric state T 1/2 =296(10)ns 62.2keV gated T 1/2 =149(6)ns 66.5keV gated 8

9 5/2- 3/2- 1/2- M1 E2 B(E2; 1/2 –  5/2 – )=22.9(4) W.u. B(M1; 3/2 –  5/2 – )=2.2(5)*10 -4 W.u. Energy[keV]α (E2)α(M1) 4.3-68.5 62.23.760.2 66.52.850.163 75 Cu- possible decay schemes 5/2- 1/2- 3/2- M1 E2 M1 Scenario A Scenario B 62.2 66.5 62.2 Shell model calculation : B(E2)=19.9 W.u. for 62.2keV transition B(M1)=0.009 W.u for 62.2keV transition Estimation for internal conversion coefficients T. Kidebi et al., Nucl.Instrum. Methods A 589(2008) 9 B(E2; 1/2 –  5/2 – )=7.89(5) W.u. B(M1; 3/2 –  5/2 – )=1.51(4)*10 -4 W.u. Energy[keV]I rel (M1)I rel (E2) 4.3(4)keV100(6) 66.5(4)keV71(5)18(2) Systematics of the energies of the 1/2 - 5/2 - states in 63-73 Cu

10 78 Ga : gamma spectrum Energy[keV]Nb. of countsI rel 157.5(2)4011(94)21(7) 211(5)815(47)5(2) 218.4(2)15533(135)100(8) 498.9(8)643(41)1.9(3) E(keV) J.-M. Daugas PhD thesis (1999) E. Mane et al., Phys. Rev. C 84(2011) 2- 60.2(2) 157.5(2) 218.4(2) 281.3(2) 341.3(3)498.9(8) 10 211(5)

11 78 Ga:time spectra 211keV new transition E(keV) T1/2= 111(2)ns 280keV gate T1/2= 110(5)ns 211keV gate T(ns) Background subtraction Fit function: convolution between a Gaussian and an exponential function Same half-life Feeding from the isomeric state-> 6.6(3)keV transition between the two state Coincidence spectra gated on 281.4keV transition -> 211+2281.4=492.4(3)keV energy of the decaying state 11

12 78 Ga: transition probabilities 499  keV transition (1.33*10 -5 s)  B(E1)= 1.35(7)*10 -9 W.u  B(E2)= 2.88(2)*10 -4 W.u  B(E3)= 1.36(5)*10 -2 W.u  B(M1)= 5.52(3)*10 -8 W.u  B(M2)= 1.33(7)*10 -1 W.u  B(M3)= 8.08(4)*10 3 W.u 157.4  keV transition (9.78*10 -7 s)  B(E1)= 1.27(3)*10 -7 W.u  B(E2)= 3.96(1)*10 -1 W.u  B(E3)= 1.87(5)*10 6 W.u  B(M1)= 7.55(2)*10 -6 W.u  B(M2)= 1.82(5)*10 2 W.u  B(M3)= 1.11(4)*10 8 W.u 218 keV transition (2.03*10 -7 s)  B(E1)= 3.58(7)*10 -7 W.u  B(E2)= 4.02(2)*10 -1 W.u  B(E3)= 9.95(5)*10 5 W.u B(M1)= 1.47(3)*10 -5 W.u  B(M2)= 1.85(4)*10 2 W.u  B(M3)= 5.92(4)*10 7 W.u 6.6 keV (211 keV) transition (3.99*10 -6 s)  B(E1)= 4.55(3)*10 -7 W.u  B(E2)= 3.58(2)*10 -2 W.u  B(E3)= 9.46(2)*10 4 W.u  B(M1)= 1.23(2)*10 -6 W.u  B(M2)= 1.65(3)*10W.u  B(M3)= 5.63(8)*10 6 W.u 12 Energy[ keV] BR[%] 157.5(2)15.4(4) 6.6(3)3.7(1) 218.4(2)73.9(19) 498.9(8)1.3(2)

13 New spin and parity assignments 2- 4- 2+ 1+E2 M2 g.s 281.3 341.3 492.3 498.9 Proposed level scheme for 78 Ga 13 M2 P.C. Srivastava,J.Phys.G39(2012 ) Jj44b ->better match with the data overall Predicts the gradual drop in 2 - energy from 74 Ga to 78 Ga Same proton configuration as 72,74 Cu

14 Summary 75 Cu New parity and spin assignments New level scheme based on γ-γ coincidences results 78 Ga New observed level :492.3(3) keV New parity and spin assignments Partial agreement with theoretical models 14

15 Thank you Acknowledgments We are grateful for the technical support provided to us by staff at the GANIL facility. The author C.Petrone is grateful for the financial support from the European Social Fond through POSDRU 107/1.5/S/80765 Project. 15


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