Study of isomeric states using gamma spectroscopy around N=40

C. Petrone1,2, J. M. Daugas3, M. Stanoiu1, F. Negoita1, G. Simpson4, C. Borcea1, R. Borcea1, L.

Caceres5, S. Calinescu1, R.Chevrier3, L. Gaudefroy3, G. Georgiev6, G. Gey4, C. Plaisir3, F.

Rotaru1, O. Sorlin5, J. C. Thomas5

1 Horia Hulubei National Institute for Physics and Nuclear Engineering, P.O. Box MG-6, 077125

Bucharest- Magurele, Romania2 Faculty of Physics, University of Bucharest - P.O. Box MG 11, RO 77125, Bucharest-Magurele,

Romania, EU3 CEA, DAM, DIF, F-91297 Arpajon, France

4 ILL, 38042 Grenoble Cedex, France5 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

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 66Fe vanishing• Isomeric state in 67Fe M.Sawicka et al.,

Phys.Rev.C 77,054306(2008)

Nuclear structure of neutron-rich nuclei lying between 68Ni and 78Ni-> modelization of astrophysical processes

2

67Fe

The key role of the role of the g g9/2 9/2 for 40 < N < 50for 40 < N < 50

f7/2

f5/2p3/

2

g9/2

28

40

50

75Cu

Neutron-rich Cu isotopes (Z=29):1 outside Z=28 core interacting with g9/2

Spin-isospin interactionTensor force

N = 46 (75Cu): f5/2 g.s. configuration K.Flanagan , Phys. Rev.C80(2009)

J.-M. Daugas Phys.Rev.C 81 (2010) 86Kr on Ni target 2 isomeric states

1|2- 1096

1|2- 454

1|2- 135 1|2-

3

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 86Kr @ 60 MeV/u on Be (500um)•Beam intensity: 4 Ae

Implantation foil (Kapton) 75 umEffective thickness = 219 um

Veto detector: Double Side Strip

Si detector

Al degrador

4

Compact reaction chamber

-> high efficiency detection

Identification matrix

5

78Ga31+

75Cu29+ +72Cu28+

Z

AoQ

ΔE, ToF, Bρ

Delayed γ-ray correlations

75Cu gamma spectrum

E(keV)

J.M.Daugas et al., Phys.Rev.C 81(2010)

66.5

(4)k

eV

62.2

(4)k

eV

T(ns)

66.5keV transition

62.2keV transition

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Energy[keV] Number of counts

Nb. of counts corr. by eff

62.2(4)keV 2483(46) 26989(143)

66.5(4)keV 2220(47) 23053(122)

γ-γ coincidences

E(keV)

E(keV) E(keV)

72Cu 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-

4-

3-

2-

Coincidence spectra 66.5keV gated

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Gamma times

• Fit function: convolution between a gaussian and an exponential

T(ns)

T(ns)

Almost 100%feeding from the uppper isomeric state

T1/2=296(10)ns62.2keV gated

T1/2=149(6)ns66.5keV gated

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5/2-

3/2-

1/2-M1

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

62.2 3.76 0.2

66.5 2.85 0.163

75Cu- possible decay schemes

5/2-

1/2-

3/2-M1

E2

M1

Scenario A Scenario

B

62.2

66.5 66.5

62.2

Shell model calculation :B(E2)=19.9 W.u. for 62.2keV transitionB(M1)=0.009 W.u for 62.2keV transition

Estimation for internal conversion coefficients T. Kidebi et al., Nucl.Instrum. Methods A 589(2008)

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• B(E2; 1/2– 5/2–)=7.89(5) W.u.• B(M1; 3/2– 5/2–)=1.51(4)*10-4W.u.

Energy[keV] I rel(M1) I rel (E2)

4.3(4)keV 100(6) 100(6)

66.5(4)keV 71(5) 18(2)

Systematics of the energies of the 1/2-

5/2- states in 63-73Cu

78Ga : gamma spectrumEnergy[keV] Nb. of counts Irel

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)

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211(

5)

78Ga:time spectra

211keV new transition

E(keV)

T1/2=111(2)ns280keV gate

T1/2=110(5)ns211keV gate

T(ns)

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

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78Ga: transition probabilities499keV transition (1.33*10-5 s)

B(E1)= 1.35(7)*10-9 W.u B(E2)= 2.88(2)*10-4W.u B(E3)= 1.36(5)*10-2 W.u B(M1)= 5.52(3)*10-8W.u B(M2)= 1.33(7)*10-1W.u B(M3)= 8.08(4)*103W.u

157.4keV transition (9.78*10-7 s)

B(E1)= 1.27(3)*10-7 W.u B(E2)= 3.96(1)*10-1W.u B(E3)= 1.87(5)*106 W.u B(M1)= 7.55(2)*10-6W.u B(M2)= 1.82(5)*102W.u B(M3)= 1.11(4)*108W.u

218 keV transition (2.03*10-7 s)

B(E1)= 3.58(7)*10-7W.u B(E2)= 4.02(2)*10-1W.u B(E3)= 9.95(5)*105W.u• B(M1)= 1.47(3)*10-5W.u B(M2)= 1.85(4)*102W.u B(M3)= 5.92(4)*107W.u

6.6 keV (211 keV) transition (3.99*10-6 s)

B(E1)= 4.55(3)*10-7W.u B(E2)= 3.58(2)*10-2W.u B(E3)= 9.46(2)*104 W.u B(M1)= 1.23(2)*10-6W.u B(M2)= 1.65(3)*10W.u B(M3)= 5.63(8)*106W.u

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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)

New spin and parity assignments

2-

4-

4-

2+

1+E2E2 E2 M2

g.s

281.3

341.3

492.3498.9

Proposed level scheme for 78Ga13

M2

P.C. Srivastava ,J.Phys.G39(2012)

•Jj44b ->better match with the data overall•Predicts the gradual drop in 2- energy from 74Ga to 78Ga•Same proton configuration as 72,74Cu

Summary75Cu• New parity and spin assignments• New level scheme based on γ-γ coincidences results

78Ga• New observed level :492.3(3) keV • New parity and spin assignments• Partial agreement with theoretical models

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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.

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