Lifetime measurement in 74Ni:probing the core polarisation around the double magic 78Ni

G. de Angelis, D.R. Napoli, E. Sahin, J.J. Valiente-DobonINFN, Laboratori Nazionali di Legnaro, Legnaro, Italy

S. Aydin, D. Bazzacco, E. Farnea, S. Lenzi, S. Lunardi, R. Menegazzo, D. Mengoni, F. Recchia, C. Ur

Dipartimento di Fisica and INFN, Sezione di Padova, Padova, Italy

P. Boutachkov, C. Domingo-Pardo, J. Gerl, M. Gorska, E. Merchan, S. Pietri, H.J. Wollersheim

GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, Germany

M. Bostan, N. Erduran, A. KusogluUniversity of Istanbul, Istanbul, Turkey

M. Doncel, B. QuintanaUniversity of Salamanca, Spain

A. Algora, A. Gadea, T. Huyuk, B. RubioIFIC Instituto de Fisica Corpuscular, Valencia, Spain

2

Scientific motivation

Inversion of the single particle orbitals

Particle-hole excitations across the shell gap (Z=28)

neutrons in g9/2

68Ni 78Ni

Z=28

T. Otsuka et al. PRL 95, 232502 (2005)

f5/2

f7/2

proton neutron

g9/2

N=50

• Study the tensor part of the (spin-isospin term of the) residual interaction.

• Attraction between orbitals with antiparallel spin configuration.

• Smaller Z=28 gap for protons in the pf-shell, and inversion of single-particle orbitals.

Z=28

j>

j>

j<

3

Scientific motivation

f5/2

f7/2

proton neutron

g9/2

N=50

j>

j>

j<

68Ni70Ni72Ni74Ni76Ni78Ni

• Study the tensor part of the (spin-isospin term of the) residual interaction.

• Attraction between orbitals with antiparallel spin configuration.

• Smaller Z=28 gap for protons in the pf-shell, and inversion of single-particle orbitals.

J.van de Walle et al., Phys. Rev. Lett. 99, 142501 (2008).

Z=28

Zn

0 2 4 6 8 10 g9/2

4

B(E2:2+0+)

~200 e2fm4

72Ni

~2 ps

70,72Ni Isotopes at LN Legnaro Core polarization due to the tensor mechanism around 78Ni

70Ni 72Ni

LNL, Multi-nucleon Transfer

Reactions

O. Perru et al. PRL 96, 232501 (2006)O. Sorlin et al. PRL 88, 092501 (2002)A. Ansari, P. Ring, PRC 74, 054313 (2006)

Eda Sahin*, Maria Doncel**, Andreas Görgen*** et al.

* INFN-LNL, Legnaro (PD), Italy** LRI, University Salamanca, Spain***CEA, Saclay,IRFU/SPhN, France

Lifetime measurement in neutron-rich

Ni, Cu, and Zn isotopes

• neutron polarization charge of 1.5 e is needed in the SM calculation in order to reproduce the experimental results!

5

74Ni at AGATA@GSI Core polarization due to the tensor mechanism around 78Ni

70Ni 74Ni

O. Perru et al. PRL 96, 232501 (2006)O. Sorlin et al. PRL 88, 092501 (2002)A. Ansari, P. Ring, PRC 74, 054313 (2006)

86Kr

1x1010pps

75Cu

100 pps 74Ni* + p

75Cu

Line shape effect of first 2+ in 74Ni vs. lifetimeRealistic MC Simulation of a fragmentation experiment: DSAM Analysis

75Cu @ 150 MeV/u

Fe Target (500mg/cm2)

74Ni

0+

2+

1024 keV

74Ni

= 0.5 to 1.5 ps

= ?

Zoom

Summary & Outlook

• The aim of the experiment at GSI would be to make one step further, compared to the present experimental programme at LNL (on the Ni, Cu and Zn isotopes), and measure the lifetime of 74Ni via the DSAM technique.

• Such measurement will represent the closest measurement to 78Ni in the seniority parabola scheme of B(E2) vs. Neutron Number, and will allow for a more detailed undertanding of the core polarisation mechanism and the tensor component of the spin-isospin term in the residual interaction.

• We think that this is a GSI-AGATA unique experiment, because of the high secondary beam intensities required to populate the 2+ in 74Ni, and because of the high angular sensitivity needed for the DSAM analysis.

8

82Se + 238U @ 515 MeV CLARA-PRISMA ΘPRISMA=ΘGrazing=64˚

Deep-inelastic and multi-nucleon transfer reactions

71Cu

73Cu

75Cu

Cu IsotopesEvolution of the Z=28 shell closure

g9/2

p3/2

f5/2

p1/2

p3/22+ (A-1Ni)

3/2-

5/2-

1/2-

7/2-

67Cu38

7/2-(f7/2)-1

69Cu4071Cu42 73Cu44

75Cu46

f5/2-p3/2 inversion

1f7/2

2p3/2

1f5/2

2p1/2

1g9/2

N=40

Z=28

K.T. Flanagan et. al, PRL 103, 142501 (2009)

Nuclear spin and magnetic moment measurements @ ISOLDE proved the inversion

9

Coulomb excitation with radioactive beams at

REX-ISOLDE

Cu IsotopesEvolution of the Z=28 shell closure

NiCu

71Cu73Cu

~2 ps

B(E2) values are essential in order to characterize the levels.

Single-particle excitations across the Z=28 shell gap will provide the information on the Z=28 shell gap size and therefore, its evolution.

p3/22+

N-50

Z=28

f5/22+p3/22+(f7/2)-1

~2ps

~2ps~25ps

~10ps

10

excitation probability depends on transitional matrix element 2+M(E2)0+ B(E2;0+→2+) diagonal matrix element 2+M(E2)2+ Qs(2+)

20 ps

28.5 ps25 ps

74Zn

2+

0+

Mf

J. Van de Walle et al., PRL 99, 142501 (2007) PRC 79, 014309 (2009)

Coulomb excitation of radioactive Zn at ISOLDE integral measurement of excitation probability relative to target excitation

B(E2) values extracted under the assumption that Qs(2+) = 0

combine Coulomb excitation and lifetimes find correct B(E2) value AND quadrupole moment

combine Coulomb excitation and lifetimes find correct B(E2) value AND quadrupole moment

Zn isotopesShape and collectivity

11

Proposed Experiment

Multi-nucleon transfer reactions

76Ge + 238U @ E(76Ge)=500 MeV

SETUP: AD coupled to PRISMA (at 59) + Köln Plunger

AIM: To measure the lifetime of the excited states in 70,72Ni, 71,73Cu, and 72-76Zn isotopes using RDDS technique

beam target degrader

12

AGATA Demonstrator vs. CLARA

A novel technique that combines the RDDS method with CLARA-PRISMA has been successfully performed using deep-inelastic reactions

AGATA

CLARA

M.C. Simulations (by D. Mengoni)

48Ca 310MeV + 208Pb

for lifetime measurement gain ~ 5

Comparison between the Diff.plunger lifetime experiment performed with CLARA and with the AGATA D.

Distances

Energy of the Projectile-like ions

<E>= 320 MeV

=28.5 m/ps =9.5%

Lifetimes (ps) Distances (m)

2 30, 60, 120, 250*

25 500, 1000, 2000

14

Rate Evaluation

70Zn + 238U @ 460 MeV CLARA-PRISMA ΘPRISMA=ΘGrazing=64˚

~100 counts

70Zn+238U

76Ge+238U (-4p)

(-3p,-2n)

(-3p)

(-2p,+2n)

66Fe

65Co

67Co

70Ni

72Ni

71Cu

73Cu

76Zn

7070Zn+Zn+238238UU 7676Ge+Ge+238238UU GAINGAIN

Beam TimeBeam Time 7 days7 days 14 days14 days 22

Beam IntensityBeam Intensity 2 pnA2 pnA 2 pnA2 pnA 11

Target Target ThicknessThickness

1 mg/cm1 mg/cm22 2 mg/cm2 mg/cm22 22

at 1 MeV (%) at 1 MeV (%) (CLARA) 2.6 (CLARA) 2.6 (AD) 6(AD) 6 ~2~2

Total Gain Factor : 8Total Gain Factor : 8

30

60

120

250

500

1000

2000

Sh

ort

L

on

gDistance (m)

Thanks to S. Lenzi

15

Beam Time Request

Beam : 76Ge at 500 MeV provided from the Tandem-ALPI complex

Target : 2 mg/cm2 238UDegrader : 4 mg/cm2 natural MgBeam Intensity: 2 pnACross sections from the GRAZING code (N. Pollarolo et. al)

(72Ni) ~ 100 µb (66Fe) ~ 100 µb (73Cu) ~ 750 µb(71Cu) ~ 250 µb(76Zn) ~ 2000 µb

14 days of beam time

(2 days per distance)

Thank you …

17

RDDS experiment in inverse kinematics: VAMOS EXOGAM – Plunger

beam: 238U, 6.5 MeV/utarget: 64Ni, 1.5 mg/cm2

degrader: Mg, 4.7 mg/cm2

6 distances: 40 – 750 μm~18 hours per distance

62Fe

64Fe

J. Ljungvall et al., to be published

18

AGATA Demonstrator vs. EXOGAM

Exogam

AD at 14cm

AGATA Demo.

118011 cm

GEANT 4 simulationand AGATA tracking(J. Ljungvall)

313514.5 cm

EXOGAM data

gain: factor 3 in singles more exotic reaction channels factor 10 in - coinc. higher precision in strong channels