Shell and Shape effects investigated at (REX) ISOLDE

CERN, ISOLDE, 5th October Elisa Rapisarda, KULeuven

Shell and Shape effects investigated

at (REX) ISOLDEElisa Rapisarda


126

82

50

50

28

20

828

The richness of Nuclear properties

82

N=Z


CERN ISOLDE Isotope Separator On-Line DEvice

ISOLDE:• delivers high-quality beams of a wide range of radioactive isotopes• unique position world-wide• post-acceleration of the existing ISOLDE beams with REX-ISOLDE up to 3 MeV/u

RILIS: Resonant Ionization Laser Ion Source


MINIBALL ISOLTRAP

GLM GHM

CRISCOLLAPSE

WITCH

WINDMILL

CERN ISOLDE Isotope Separator On-Line DEvice


Down & Up Along the Nuclear Chart

82

50

126

82

50

28 Evolution of Shell structure• Coulomb Excitation Cu, Zn, … ;• Transfer reaction (d,p), (3He,p);• - decay of Mn, Fe, Co, Ni, …;• Laser spectroscopy Co, Ni, Cu, …;• Mass measurements

Shape-coexistence•Coulomb Excitation Hg, Po, Pb, Ra, Rn;• +/EC of Pb, Tl;•Laser spectroscopy Po, Pb, Tl;•-decay•Mass measurements

N=40

N=104


N=40 and Coulex of the Cu isotopes

high E(2+) in 68Ni (R. Broda et al., PRL 74 (95) 868) low B(E2, 0+ 2+) (Sorlin et al., PRL 88 (2002))

proposed new magic number N=40

n-rich Cu isotopes provide an excellent means for testing the proton-neutron residual interaction in this mass -region;

2003 Mass measurement ISOLTRAP and β-decay;

2005-2008: Coulomb excitation of odd-odd 68,70Cu;

2006: Coulomb excitation of odd-mass 67,69,71,73Cu.

N=4

0 N=5

0

Coulomb excitation of isomeric states of 70Cu


The odd – odd 70Cu

70Cu: J. Van Roosbroeck et al., PRL92(2004)112501, J. Van Roosbroeck et al., PRC69(2004)03431370Cu: J. D. Sherman et al., Phys.Lett. B67(1977)27568,70Cu: I. Stefanescu et al., Phys.Rev. Lett 98(2007)122701

0

228

242

T1/2= 33 s

506 (10)

T1/2= 6.6 s

6-

3-

4-

1+

(5-)

70Cu41-

T1/2= 45.5 s

101

E2

the low-energy level schemes dominated by multiplets originating from the coupling of the odd proton with the odd neutron p3/2 g9/2 = 3-, 4-, 5-, 6- or p3/2 p1/2 = 1+, 2+

B(E2) values within the states of the p3/2 g9/2 multiplet offers important information about the p-n residual interaction across N=40.

g9/2

f7/2

40

llllllll llllllll

llllllllll

l

p3/2

f5/2

p1/2

l

2828

70Cu41

ll

V. Paar Nucl.Phys.A331(1979)16


Mass Measurement, -decay

Transfer reaction 70Zn(t,3He)70Cu

Coulomb Excitation


Isomeric Beams from REX-ISOLDE

technique based on in-source laser spectroscopy

(Ü. Köster et al., NIM B, 160, 528(2000); L. Weissman et al., PRC65, 024315(2000)).

set the laser frequency to select and maximize the production of the isomer of interest.

+ postacceleration by REX-ISOLDE

6- (g.s.)

1+

70Cu 3-

6-

1+

0

242

3-

101

J. V

an R

oosb

roec

k et

al.,

PRL

92(2

004)

1125

01



Experimental details6- (g.s.)

1+

70Cu 3-

6-

1+

0

242

3-

101

Isomeric Composition determined from characteristic beta decay lines

70Cu on 120Sn

Beam energy: 2,83 MeV/u

Beam Intensity: 5 X 105 pps

disentangle (6- XXX) and (3- XXX)

Inclusive excitation cross-sectionInclusive excitation cross-section

70Cu/70Ga = 80%/20%70Cu:

6- 86% 3- 7%1+ 7%

70Cu/70Ga = 50%/50%

70Cu:6- 72% 3- 25%1+ less than 3%

68,70Cu: I. Stefanescu et al., Phys.Rev. Lett 98(2007)122701



70Ga contamination

The separator is not able to separate 70Cu from 70Ga

70Ga and 70Cu impinges both on target

Laser ON – Laser OFF to disentangle Cu interaction from Ga interactions

Laser ON 70Cu + 70Ga

Laser OFF 70Ga

Ga contribution can be precisely subtracted provided a precise normalization of Laser ON laser OFF run

Laser ON-OFF mode



Experimental Setup

70Cu 2,9 MeV/u on 120Sn 2,3 mg/cm2

REX-ISOLDE

Coulomb excitation of isomeric states of 70CuCoulomb excitation of isomeric states of 70Cu


127 keV

511 keV

Coulomb Excitation of 70,gsCu and 70,m1Cu

6-

3-

4-

5-

0101

228127 (M1)

E2

E2

511 (M1)

A=70DC

A=120DC

1171 keV

(506) 511



Cross Section: 127 KeV

DC for A=7070Cu (4- 3-)

127 keV

• CLX code• Matrix element = 0.23(3) eb•B(E2, 3- 4- ) = 73(10) e2 fm4

• CLX code• Matrix element 0.30(4) eb•B(E2, 6- 4- ) = 69(9) e2 fm4

Measurement of the (4- 3-) cross section in both experimentsIsomeric Composition of the 70Cu beam is known Disentangle the (6- 4-) and (3- 4-)

6-

70Cu

3-

4-

5-

0 T1/2= 44.5 s

101 T1/2 = 33 s

228

511

127 keV


CEd

B(E2 : 0 2 )d


Challenge to measure

Cross-Section 511 KeV

6-

70Cu

3-

4-

5-

0 T1/2= 44.5 s

101 T1/2 = 33 s

228

(506) 511 511 keV

???

DC for A=7070Cu (5- 6-)

511 keV

• CLX code• Matrix element 0.308(19) eb• B(E2, 3- 5- ) = 136(15) e2

fm4

Assuming only (3- 5-) excitations

Upper Limit



Z=28 N=28

• realistic interaction (M. Hjorth-Jensen et al. , Phys.Rep.26(2004)

• model space is 1f5/22p3/22p1/21g9/2 outside the 56Ni

inert core;

SMI Calculations by N. Smirnova

Shell Models: comparisonLarge Shell-Model calculations with ANTOINE code

• hybrid interaction (S.Lenzi et al., PRC82, 05430(2010)) + evolution of the proton gap from 68Ni to 78Ni;

• model space is 1f7/21f5/22p3/22p1/2 for protons and

1f5/22p3/22p1/21g9/22d5/2 for neutrons outside the 48Ca inert

core;


SMII Calculations by K. Sieja

1g9/2

2p1/2

2p3/2

1f5/2

• NO proton-core excitations

• NO neutron-core excitations

Systematics of the 6- 4- transition

Z=20 N=28

2p1/2

2p3/2

1f5/2

1f7/2

2d5/2

Neutrons excitations across N=50

Proton excitations across Z=28

1g9/2


82

50

126

82

50

28

Shape-coexistence

Down & Up Along the Nuclear Chart

Shell structureN=40


A classical example: 186Pb

o Shape coexistence = proximity of spherical and/or deformed shapes(s) at low energy (E < few MeV)o 186Pb: most dramatic examples where the three lowest lying states are 0+ states of three different shapes within less than 700 keV.

A.N. Andreyev et al., Nature 405(2000)430

0+ 0+ 0+

Probe shape-coexistence in 182Hg via -decay of 182Tl


Shape coexistence in Hg isotopes

Evidence for shape coexistence in systematic

energy levels: flat behaviour of the spherical

states against parabolic intrusion of the

deformed states with a minimum at mid-shell

N = 104.

slightly oblate ground state band

excited prolate band

Mid-shell N = 126


2008: Coulomb excitation of even-even 182-184-186-188Hg;

2010-2011: -decay and laser spectroscopy of odd-odd 178-180-182-184-186Tl;

2010-2011: laser spectroscopy of odd-even 179-181-183-185-187Tl;


Reorientation in Coulomb Excitation

0+

2+

The cross section for exciting the 2+ state DOES NOT only depend on its reduced transition probability B(E2: 0+ -> 2+), but also on the diagonal matrix element <2+||M(E2)||2+>.

CEd

B(E2 : 0 2 )d



0+

2+

Obtain sensitivity on the diagonal matrix element of the first excited state by scanning the center of mass angular range!

Coulomb Excitation of 182,184, 186,188Hg

The detected γ yields of the photo peaks can be used to extract:• transitional matrix elements (B(E2) values)• diagonal matrix elements (quadrupole moments)

Program GOSIA: by fitting the matrix elements to produce the obtained γ yields by a χ2 minimization. (T. Czosnyka et al, GOSIA2)

Measurement of the nuclear shapes DIRECTLY

To help fit:• precise level scheme;• decay properties (E0 component);• lifetime measurements



Spectroscopy methods

in beam

182Tl 182Hg 186Pb 190Po

T. Grahn et al. PRC80(2009) 014324

h.s.l.s.

decay

0+

2+

4+

0+

N. Bree & A. PettsCoulex

2+

4+

6+

0+

0+

0+

J. Heese et al. PLB302(1993) 390

0+

decayA. Andreyev et al. Nature 405 (2000) 430

Transfer reactions

Ground State propertiesMass measurements (direct, decay)

Laser Spectroscopy

T. Cocolios et al. PRL106(2011) 052503H. De Witte et al. PRL98(2007) 112502

What are the observables (“Shape coexistence in atomic nucleus”, K.Heyde and J.Wood, Rev.Mod.Phys., in press)

E0 component

180Hg, J.Elsevier et al., PRC 84, (2011) 034307



t1/2=2.6s

178Au182Hg

b+/EC a

gg

a

178Pt

b+/EC

182Au

4%

(15%) (85%)

t1/2=3.1s

t1/2=10.8s

t1/2=15.6st1/2=21.1s

182Tl

97.5%

-decay spectroscopy

182Tl101

= 101

1g7/2

2d5/2

1h11/2

2d3/2

3s1/2

1h9/2

2f7/2

1h9/2

1i13/2

3p3/2

2f5/2

2g9/2

3p1/2

= 81

50

82126

82

3s1/2 1i13/2 = 6+, 7+ or

3s1/2 1h9/2 = 4-, 5- or

3s1/2 3p3/2 = 1-, 2-

1h9/2 i13/2 = (2-, 11-)

ISOMERISM in 182Tl?

KEY FEATURES- Decay dominated by selection rule: l = 1,0-low-lying non-yrast coexisting states-E0 component of intraband transition

E0 component

?

[1] K.S. Bindra et al., Phys. Rev. C, 51 (1995) 401



-spectroscopy: Experimental Setup

Windmill Chamber

Annular Si Si

pure 30 keV Tl beam from RILIS+ISOLDEIntensity = 104 pps

C-foils20 mg/cm2

Si detectors

SiAnnular Si

ff

ff

a

30 keV beam from ISOLDE

C-foil

Ge detector #1

Courtesy of Thomas E. Cocolios



and Si- coincidences

g1 - g2 coincident:

or

g1

g1g2

g2Gamma coincidences with 8+ 6+ (413.2 keV)

E0 K-component 335KeV Si coincidences with 639 keV

g1 = 639 keV

E0



Result: infer ground state of 182Tl

s1/2 i13/2 = 6+, 7+ or s1/2 h9/2 = 4-, 5- or s1/2 p3/2 = 1-, 2-

*

**

*

**

**

*****


[1] K.S. Bindra et al., Phys. Rev. C, 51 (1995) 401

f7/2

h9/2

i13/2

p3/2

f5/2

g9/2

p1/2

g7/2

d5/2

h11/2

d3/2

s1/2

h9/2

= 81

50

82

= 101

126

82


Result: , and level mixing +20 +

32+20 state: 335 keV

- identified by looking at Si-g coincidences- already placed at 328 (12) keV from -decay of

186Pb [1]

- g rays coincident with this Si energy: 639 keV

182Hg0+

0+2+

2+

4+

(2+)

8+

0

335351548612

973

1358

548

213

197

9446+

1124(4+)

E0

+22 +2 transition: 197 keV

- important E0 component (ICC = = 4.2 (8))

- the two levels are mixed;- the two levels have different deformation

CEII

Evidence for shape coexistence: transitions with E0 components are a model-independent signature of the mixing of configurations with different

mean-square radii

[1] J.Wauters et al., Phys. Rev. C, 50 (1994) 2768

+24 state: 1124 keV

- suggested in [2] but the 772.6 transition could not be seen

- from the energy systematics of the even-even Hg isotopes is a good candidate for 4+ member of the oblate

band[2] M. Scheck et al., Phys. Rev. C, 81 (2010) 014319

639

621.9 772.6

576.6

state: 973 keV- based on unambiguous coincidence relations- band-head of vibrational band on top of prolate

band- (621.9 keV): no E0

component

+32

+

32 +

22


180Hg, J.Elsevier et al., PRC 84, (2011) 034307


82

50 126

82

50

28

N=40

Shape-coexistence

But new possibilities arise: ‐ multiple Coulomb Excitation ‐ transfer reactions ‐ spins, moments and radii measurements in previously hardly accessible regions

Although we have different experimental probes at our disposition, we still do not have a full picture of many phenomena

Down & Up Along the Nuclear Chart… a large world to explore


IKS Leuven, Belgium - I. Stefanescu, J. Diriken, N. Bree, M. Huyse, O. Ivanov, J. Van de Walle, P. Van Duppen

IPN Orsay, France - S. Franchoo

CSNSM Orsay, France - G. Georgiev, E. Fiori, R. Lozeva

IKP Köln, Germany A.Blashev, B.Bruyneel, J.Eberth, Ch.Fransen, K. Geibel, H.Hess, J.Jolie, M.Kalkuehler, P.Reiter, M.Seidlitz, N.Warr

TU München, Germany - Th. Kröll, R. Krücken, K. Wimmer

University of Camerino, Italy - D.L. Balabanski, K. Gladnishki, G. Lo Bianco, S. Nardelli

Warsaw University, Poland - J. Iwanicki, K. Hadynska, K. Wrzosek, M. Zielinska, J. Srebrny

University of Edimburg, Scotland – T. Davinson

Universiteit Ghent, Belgium - K. Heyde, N. Smirnova

CERN, Geneva, Switzerland - P. Delahaye, D. Fedorov, V. Fedosseev, U. Köster, B. A. Marsh, F. Wenander

and the ISOLDE and MINIBALL collaborations

Collaboration

Acknowledgement: Marie Curie Intra-European Fellowship of the EC’s FP7

IKS Leuven, Belgium - I. Darby, J. Dirichen, J. Elseviers, N. Bree, M. Huyse, D. Pauwels, D. Radulov, P. Van de Bergh, P. Van Duppen

University of West Scotland, UK – A.N. Andreyev, V. Liberati, Joe

Comenius University, Bratislava, Slovakia - M. Venhart, S. Antalic, M. Veselsky, Zdenka

University of Manchester, UK – I. Tsekhanovich

University of Ioannina, Greece – N. Patronis

Institute Laue Langevin, Grenoble, France - U. Köster

CERN, Geneva, Switzerland – T. E. Cocolios, V. Fedoseev, B. A. Marsh, M. Seliverstov, Anatoly, Pavel

Documents

Shell and Shape effects investigated at (REX) ISOLDE