Measurements of competing structures in neutron-deficient ...€¦ · Measurements of competing structures in neutron-deﬁcient Pb isotopes by employing Coulomb excitation Spokespersons:

Physics background Update on the analysis method Proposed experiment

Measurements of competing structures inneutron-deficient Pb isotopes by employing

Coulomb excitation

Spokespersons:Tuomas Grahn

Janne Pakarinen

University of Liverpool, UK&

Collaborators

INTC meetingFebryary 16, 2009

T. Grahn (University of Liverpool) Pb CoulEx INTC 1 / 18


Outline

1 Physics background

2 Update on the analysis method

3 Proposed experiment



Chart of nuclides in the vicinity of light Pb nuclei

Hg 184

104

83

84

82

81

80

Bi 187 Bi 188 Bi 189 Bi 190 Bi 191

Pb 189Pb 188Pb 187Pb 186Pb 185Pb 184

Bi 185

Pb 183Pb 182Pb 181Pb 180

Tl 179 Tl 180 Tl 181 Tl 182 Tl 183 Tl 184 Tl 185 Tl 186

Hg 185Hg 183Hg 182Hg 181Hg 180Hg 179Hg 178Hg 177Hg 176Hg 175Hg 174

Bi 186

Po 190 Po 191 Po 192

decay decay

Alpha

decay

Beta + Proton

Tl 178Tl 177

Pb 178 Pb 179

Tl 176

Hg 173Hg 172Hg 171

Bi 184

Po 189Po 188

Pb 190

Po 193 Po 194

Pb 192 Pb 193 Pb 194Pb 191

Bi 192 Bi 193 Bi 194 Bi 195 Bi 196

Tl 188 Tl 189 Tl 190 Tl 191 Tl 192

Po 195 Po 196 Po 197 Po 198

Hg 186 Hg 187 Hg 188 Hg 189 Hg 190

Tl 187

Nucleus

interestof

Unique laboratory to study shape-coexistence phenomena

Many spectroscopic techniques to investigate these isotopes(β and α decay, in-beam γ-ray, isomer, trap-assisted spectroscopy etc.)



Level energy systematics for Pb isotopes



Triple shape coexistence in neutron-deficient Pb isotopes

See e.g. J.L. Wood et al., Phys. Rep. 215, 101 (1992).



Triple-shape coexistence in 186Pb (in-beam and decayspectroscopy)

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

J. Pakarinen et al., Phys. Rev. C 75, 014302 (2007).T. Grahn (University of Liverpool) Pb CoulEx INTC 6 / 18


Mean square charge radii of neutron-deficient Pb isotopes

H. De Witte et al., Phys. Rev. Lett. 98, 112502 (2007).



Transition quadrupole moments for yrast states in 186,188Pb

T. Grahn et al., Phys. Rev. Lett. 97, 062501 (2006).



Theoretical studies of neutron-deficient Pb nuclei

Recent studies using IBM and self-consistent mean-field approaches. B(E2)values for the 2+ → 0+ transition in 188Pb.

V. Hellemans et al.,Phys. Rev. C 77,064324 (2008).

M. Bender et al.,Phys. Rev. C, 69,064303 (2004)

R.R.Rodríguez-Guzmánet al., Phys. Rev. C,69, 054319 (2004)



Open questions related to neutron-deficient Pb isotopes

Confirmation of three different shapes in the same nucleus

Systematic behaviour of mixing between different shape coexistingstructures

Is the collectivity of the prolate yrast bands in Pb nuclei higher than thatof the identical prolate bands in Hg and Pt nuclei?

What is the validity of different models?
























Outline






Analysis - what is learnt from the Hg experiments IS452

Energy (keV)0

2 0

4 2

2 0 2

0

Cd

Hg

X−

rays

200 400 600 800 1000

Co

un

ts

0

100

200

300

400

500

600

700+

+ 1g

.s.

++ 1

1

++ 2

g.s

.

++ 1

g.s

.

11

2

Doppler-corrected γ-ray spectrum of 182Hg (IS452).

−3 −2.5 −2 −1.5 −1 −0.5 0 0.5 1 1.5 2 2.5 3

<2+||E2||2

+> [eb]

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

2.4

<0+

||E2

||2+>

[eb

]

Low COM Angular Range

Med COM Angular Range

High COM Angular Range

186Hg on

107Ag

0.0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

(0+

2+1)

[b]

0 20 40 60 80 100 120 140 160 180

COM [o]

< 2+

1 |E2 | 2+

1 > = 1 eb< 2

+1 |E2 | 2

+1 > = 0 eb

< 2+

1 |E2 | 2+

1 > = -1 eb

Extraction of the matrix elements

from the measured σCE .

Nuclear reorientation effect:σCE(Ji → Jf ) ∝ |〈Jf | Ô(E2)|Ji〉|2 · [1 − 〈Jf | Ô(E2)|Jf 〉 · f (ζ)]



Analysis - what is learnt from the Hg experiments IS452



Outline






Experimental details

Proposed measurement can only be carried out at REX-ISOLDE

RILIS + REX-EBIS + REX-ISOLDE + MINIBALL

Recent purity test of Pb beams reported the the purity of at least 80% for190,192Pb. Contaminants in 188Pb beam do not pose a problem (seeproposal)

Counts obtained in requested beam time for the 2+1 → 0+

g.s. transition

Nucleus ISOLDE Beam intensity on 〈0|| Ô(E2)||2〉 (eb) γ-ray yieldyield (µC−1) MINIBALL target (pps)

188Pb 1.7 × 106 1.7 × 104 0.475 2200190Pb 2.3 × 107 2.3 × 105 0.475 7400192Pb 4.0 × 107 4.0 × 105 0.475 10700








g.s. transition


188Pb 1.7 × 106 1.7 × 104 0.475 2200190Pb 2.3 × 107 2.3 × 105 0.475 7400192Pb 4.0 × 107 4.0 × 105 0.475 10700








g.s. transition


188Pb 1.7 × 106 1.7 × 104 0.475 2200190Pb 2.3 × 107 2.3 × 105 0.475 7400192Pb 4.0 × 107 4.0 × 105 0.475 10700








g.s. transition


188Pb 1.7 × 106 1.7 × 104 0.475 2200190Pb 2.3 × 107 2.3 × 105 0.475 7400192Pb 4.0 × 107 4.0 × 105 0.475 10700



Aims of the proposed experiment

Determine the sign of thespectroscopic quadrupolemoment of the 2+

1 states in188,190,192Pb

Probe the collectivity oflow-lying states in188,190,192Pb isotopes(spherical/oblate)

Study the mixing of the 2+

states as a function of N

0 0

2 724

4 10642 953

4 1315

0 588

724

340

953

362592

251

5−12 ps

15.9(10) ps

188Pb









2 774

0 0

4 1229

0 658

2 1163

0 0

2 854

4 1356

0 768

2 1238

455

774

389

1163

854

502

1238

384 469

190 192Pb Pb











Requested beamtime

3 shifts are requested for setting up the REX facility

12 shifts for the γ-ray yield measurement of 188Pb (9 laser on + 3 laseroff)

For the measurements of 190,192Pb, 3 shifts for each nucleus are required

21 shifts are requested in TOTAL



Collaboration

CERN-ISOLDE (J. Cederkäll, P. Delahaye, J. Van de Walle, F. Wenander)STFC Daresbury Laboratory (D. O’Donnell, J. Simpson)University of Edinburgh (T. Davinson, P. Woods)GANIL (E. Clément)University of Göttingen (K.-P. Lieb)University of Jyväskylä (P.T. Greenlees, R. Julin, S. Juutinen, P. Peura, P. Rahkila)KU Leuven (A.N. Andreyev, B. Bastin, N. Bree, J. Diriken, M. Huyse, P. Van Duppen)University of Liverpool (P.A. Butler, T. Grahn, L.P. Gaffney, T. Grahn,R.-D. Herzberg, J. Pakarinen, R.D.Page, A. Petts, M. Scheck)University of Lund (A. Ekström, C. Fahlander)LMU München (L, Csige, D. Habs, P.G. Thirolf)TU München (V. Bildstein, R. Gernhäuser, Th. Kröll, R. Krücken, K. Wimmer)University of Oslo (A. B’urger, M. Guttormsen, A.C. Larsen, H.T. Nyhus, S. Siem, N.U.H. Syed, H. Toft)CEA-Saclay (A. Görgen, W. Korten, J. Ljungvall, A. Obertelli, B. Sulignano, Ch. Theisen)University of Sofia (G. Rainovski)HIL University of Warsaw (K. Hadynska, J. Iwanicki, P. Napiorkowski, J. Srebrny, K. Wrzosek-Lipska,M. Zielinska)University of York (C. Barton, M. Bentley, D.G. Jenkins, B.S. Nara Singh, A.P. Robinson, R. Wadsworth)


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Measurements of competing structures in neutron-deficient ...€¦ · Measurements of competing structures in neutron-deﬁcient Pb isotopes by employing Coulomb excitation Spokespersons: