Structure of N~40 Ni isotopes studied by knock-out reactions

Structure of N~40 Ni isotopes studied by knock-out reactions

Francesco Recchia

UN IVERS ITÀ DEGL I STUD I D I PADOVA

Francesco Recchia – ISOLDE seminar – CERN

Overview Scientific motivation Study of Ni isotopes:

Neutron knock-out with GRETINA and S800 at NSCL

New data on 68Ni and implications for the structure of its low-spin states

2


f7/2

d3/2

d5/2

p1/2

1d

1f

s1/22s

2pp3/2

f5/2

L.SH.O L2

N=2

N=3

1g

N=4

2d

+ +

d5/2

1p

N=1

p3/2

p1/2

g9/2

The “spin-orbit” magic numbers

3

8

20

28

40

5040

20

8


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

mm’

m’D

T. Otsuka Phys. Scr. T152 (2013) 014007


The effective interaction

Mm VVV

A multipole expansion

monopole Multipole

mV- represents a spherical mean field extracted from the interacting shell model - determines the single particle energies or ESPE.

- correlations- energy gains

Deformation

MV

Tm

LSm

Cmm VVVV

5

Interplay spectacular phenomena ioi


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)

42Si

Deformed intruder configurations fall below the spherical ones

A. Poves, 2011

N=8

N=20

N=28

Si

6

11Li


Islands of inversion

32Mg20

sd

p3/2

f7/2

20

64Cr40

pf

d5/2

g9/2

40

12Be8

p

d5/2

s1/2

8

N=1

N=2

N=2

N=3

N=3

N=4

Islands of Inversion are observed at the harmonic oscillator magic numbers.

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8

68Ni region


Observables at N=40

E(2+)

B(E2)

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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)


Neutron excess and shell migration

pf7/2

np3/2

nf5/2

np1/2

ng9/2

40

32

protons

neutrons

protons0f7/2

0f7/2

1p3/2

1p1/2

0f5/2

0g9/2

neutrons

Z = 28 40

28 280f7/2

1p3/2

1p1/2

0f5/2

0g9/2

neutrons0f7/2

protons

32

Z = 20

Monopole shifts

10

• 68Ni is at the limit of region of deformation


68Ni low spin states Collective structure in 68Ni? Based on deformed excited states?

11

pf7/2

np3/2

nf5/2

np1/2

ng9/2

40

32

protons

neutrons

pf5/2

28

YES: Type II shell evolutionY.Tsunoda, T.Otsuka et al. arXiv [nucl-th]23/9/2013


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Single Particle Strength in the odd, neutron-rich Ni isotopes

Dec 8 – 12 2012

Persistence of customary magic numbers Spin-isospin part of the nn interaction Single particle strength in A-1Ni

• components in the g.s. in ANi

• comparison to shell model calculations

Provide the first gating transitions for GS data


Example: 82Se → 72Ni K500

K1200A1900

productiontarget

ion sources

couplingline

strippingfoil

wedge

focal plane

p/p = 1%

82Se13+,12 MeV/u

82Se34+,140 MeV/u

82Se 82Se 82Se

fragment yield after target fragment yield after wedge fragment yield at focal plane

72Ni 72Ni 72Ni

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Figure courtesy A. Stolz


A1900 fragment separator

Reaction product identification S800 spectrograph

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69Cu

68Ni

67Co

TOF obj

TO

F xfp

Reaction target100-281mg/cm2




15


73Cu

75Zn

72Ni

74Cu




16


67Ni*

γ

β U 0.4c

67Ni

to focal plane S800

68Ni

γ

9Be





17

67Ni

65Co66Ni

Gated on 68Ni

Velocity vector





18

K. Meierbachtol et al. NIM A 652 (2011) 668–670


68Ni is produced from 70NiA surprise in 68Ni…

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Low-spin states in 68Ni

20

1770(30)

0+

Bacchus@IPN OrsayGIROD et al. 1988



21

1770(30)

0+

Lisol@KU LeuvenMueller et al.

2000



22

1770(30)

0+

Pauwels et al. 2012

Predicted a new 0+ level at 2202 keV

N=40

Z=40



23

1770(30)

0+

2202 0+

EXOGAM-VAMOS@GANILDijon et al. 2012

2p2h



24

1770(30)

0+

2202 0+

EXOGAM-VAMOS@GANILDijon et al. 2012

GAMMASPHERE@ANL

Chiara et al. 2012

2p2h





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K. Meierbachtol et al. NIM A 652 (2011) 668–670

70Ni →68Ni

Clean P-D coincidences


A surprise in 68Ni !! <511> in the hodoscope

prompt

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Lifetime

ch

350(50) ns

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GIROD PRC 1988

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2nKO with GRETINA at NSCL…

(a) CsI(Na) spectrum, 68Ni-gated; (b) GRETINA spectrum, gate on 511 and 68Ni

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DIS experiment440-MeV 70Zn + 208Pb DIS reaction at ATLASStand-alone Gammasphere (100 Ge

detectors)

• Thick target stops all reaction products

• Beam period 412 ns

• Trigger on g fold ≥3

• DIS produces cross-coincident partner nuclei

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Analysis by CJ Chiara – University of Maryland/ANL


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 b decay of the reaction products

Ge timing

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DIS with Gammasphere at ATLAS…

(delayed Po lines)(a,b) gate 662/Po; (c) gate 662/1139

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Measured branching ratios relative B(E2)’s for decays to 0+

1,2 and 2+

1 states.

*

*W. F. Mueller et al., PRC61, 054308 (2000)

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B(E2) ratios, normalized at each level

2+2 decay

favors 2+1

(mixed)

SM calcs with 56Ni core + nf5/2pg9/2 Generally good energiesSmall ‘tweak’ B(E2) ratios from 2+

2 agree(0.4%)n(g9/2)m components...; 0+

3 no good

m=2 (68%)m=4 (29%)

m=0 (42%)m=2 (43%)

m=2 (56%)m=4 (28%)

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g9/2

p1/2

28

f5/2p3/2

50

40


B(E2) ratios, normalized at each level

2+2 decay

favors 2+1

(mixed)

• pfp + nf5/2pg9/2d5/2

• 0+3 is p excitation

• B(E2)’s reproduced• B(E2)2+

1→0+2 is 16 times B(E2)2+

2→0+2

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g9/2

p1/2

28

f5/2p3/2

50

40p1/2

28

f5/2p3/2

40

d5/2

f7/2


N. Shimuzu, T. Otsuka et al. Prog. Theor. Exp. Phys. (2012) 01A205

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MC Shell Model


MC Shell Model

Tsunoda JPG (2013), [nucl-th] 1309.5851v1 (2013)

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N. Shimuzu, T. Otsuka et al. Prog. Theor. Exp. Phys. (2012) 01A205


Conclusions 68Ni 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? 68Ni:

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


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. ZhuTheory:B.A.Brown

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Available online 2 weeks ago!


GRETINA Experiments at NSCL

Nuclear Shell Evolution• N=Z Mirror Spectroscopy

• Structure in 221,223Rn • 50-52Ca neutron knock-out

• Neutron-rich Ti • Odd neutron-rich Ni • 34Si 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 58Zn

• Measurement of the 56Ni(d,n)57Cu transfer reaction

Collective Nuclear Structure• Transition matrix elements in 70,72Ni• 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 12Be

• 71-74Ni excited-state lifetimes • Inelastic excitations beyond 48Ca Triple configuration

• coexistence in 44S • GT strength distributions in 45Sc and 46Ti

• Search for isovector giant monopole resonance

23 Expts3360 hrs

done through February 2013Prepared by H. Crawford, LBNL


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The new interaction in the fpgd space

LNPS interaction: renormalized realistic interaction + monopole corrections

48Ca core protons: full pf shellneutrons: p3/2,f5/2, p1/2, g9/2, d5/2

40

28 28f7/2

p3/2

p1/2

f5/2

g9/2

d5/2

48Ca

KB3gr for the pf-shell;

monopole corrections to reproduce the Z=28 and N=50 gaps in 78Ni based on data of neighboring nuclei

S. M. Lenzi, F. Nowacki, A. Poves, and K. Sieja, PRC82, 054301 (2010)


The N=40 isotonesE (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 orbitalsand percentage of p-h configurations

S.M. Lenzi, F. Nowacki, A. Poves and K. Sieja, PRC 82, 054301 (2010)

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The energy levels at N=40 cannot bedescribed within the fp or fpg space

420

1131

Neutron-rich Cr and Fe isotopes results and shell-model calculations

S. Lenzi, F. Nowacki, A. Poves and K. Sieja 2010

f7/2

p3/2

f5/2

p1/2

48Ca

g9/2

d5/2

68Ni

π ν

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Cr-Fe-Ni isotopes

E (2+)

B(E2)

β~0.35 β~0.3

FeCr Ni

S.M. Lenzi, F. Nowacki, A. Poves and K. Sieja, PRC 82, 054301 (2010)

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Structure of N~40 Ni isotopes studied by knock-out reactions

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