Coulomb excitation of 184,186,188HgNick Bree & Andrew Petts

Katholieke Universiteit Leuven & University of LiverpoolP.A. Butler, J. Cederkäll, E. Clement, T.E. Cocolios, L. Fraile, T. Grahn, M. Guttormsen, K. Hadynska, R.-D.

Herzberg, M. Huyse, D.G. Jenkins, R. Julin, S. Knapen, Th. Kroell, R. Krücken, A.C. Larsen, P. Marley, P.J.

Napiorkowski, J. Pakarinen, N. Patronis, P.J. Peura, E. Piselli, M. Scheck, S. Siem, I. Stefanescu, J. Van de

Walle, P. Van Duppen, D. Voulot, F. Wenander and M. Zielinska

Content

• Motivation: shape coexistence• Experimental set-up• Shape measurements by Coulomb

excitation• Preliminary experimental results• Conclusion and outlook

Coulex of 184,186,188Hg: Content

Z = 82

Coulex of 184,186,188Hg: Motivation

π

82

2d5/21h11/2

2d3/23s1/2

1g7/2

1h9/2

Coulex of 184,186,188Hg: Motivation

184HgN=104

0+

2+

4+

0+

2+4+

0

367

1089

375

534653

0+

2+

4+

0

405

1080

523621808

0+2+4+

0+

2+

4+

0+2+

4+

0

413

1005

824881

1208

186HgN=106

188HgN=108

MID SHELL

Coulex of 184,186,188Hg: Motivation

π=80

82

2d5/21h11/2

2d3/23s1/2

1g7/2

1h9/2

ν=104

126

2f7/21i13/2

3p3/22f5/2

1h9/2

3p1/2

2g9/2

E*intruder(4p-6h)=4(εjπ-εj’π) - ΔEππpair + ΔEπνM – ΔEπνQ

K. Heyde et al, Nucl. Phys. A 466, 189 (1987)

4(εjπ-εj’π)

ΔEπνQ~NπNν

2(εjπ-εj’π)

ΔEπνQ~NπNν

ΔEpairing

ΔEpairing

g.s. g.s.

Hg,Pb Pt,Po,Rn,Ra

184Hg

Slightly oblate ground state bandProlate band SHAPE COEXISTENCE

Coulex of 184,186,188Hg: Experimental set-up

θP

θD

184Hg projectile

120Sn target

bϑ P

ϑ D

Coulex of 184,186,188Hg: Experimental set-up

Isotope Charge state

Intensity@Miniball

184Hg 43+ 1000 pps

186Hg 43+ 2.0 x 105 pps

188Hg 44+ 2.5 x 105 pps

All 3 isotopes were post-accelerated by REX to 2.85 MeV/u.

Miniball

• Doppler shift in the gamma energy!

Coulex of 184,186,188Hg: Experimental set-up

θP

EP

ED

CD-detector

184Hg 2,85 MeV/u target 120Sn

2.3 mg/cm2

Coulex of 184,186,188Hg: Shape measurements

0+

2+

+ + σ⎛ ⎞→ ⎜ ⎟Ω⎝ ⎠CEdB(E2 : 0 2 )

d

The cross section for exciting 184Hg to its 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+>.

B(E2) = 19500±4500 e2fm4

N. Rud et al, PRL 31, 1421, 1973+ life time measurements

Since the B(E2) value is known, the sign and magnitude of the quadrupole moment of the 2+ state can be measured by calculating the excitation cross section out of the intensity ofthe detected γ photo peak of the 2+->0+ transition.

184Hg120Sn

184Hg

Coulex of 184,186,188Hg: Preliminary experimental results

In August 2007 a Coulomb excitation experiment was performed on the neutron deficient 184,186,188Hg isotopes.

non Doppler corrected γ spectrumDoppler corrected γ spectrum

0+

2+

4+

0

367

1089

375

534653

0+

2+4+

Coulex of 184,186,188Hg: Preliminary experimental results

In August 2007 a Coulomb excitation experiment was performed on the neutron deficient 184,186,188Hg isotopes.

non Doppler corrected γ spectrumDoppler corrected γ spectrum

0+

2+

4+

0

367

1089

375

534653

0+

2+4+

Coulex of 184,186,188Hg: Preliminary experimental results

In August 2007 a Coulomb excitation experiment was performed on the neutron deficient 184,186,188Hg isotopes.

Doppler corrected γ spectrum

0+

2+

4+

0

405

1080

523621808

0+2+

4+

403

Coulex of 184,186,188Hg: Preliminary experimental results

In August 2007 a Coulomb excitation experiment was performed on the neutron deficient 184,186,188Hg isotopes.

Doppler corrected γ spectrum

0+

2+

4+

0+2+

4+

0

413

1005

824881

1208

Coulex of 184,186,188Hg: Preliminary experimental results

Example: determination of the <2+||M(E2)||2+> matrix element in 186Hg.

0,8

1

1,2

1,4

1,6

1,8

2

-2 -1 0 1 2 3

<2+1||E2||2+

1> [eb]

<0+ g.

s.||E

2||2+ 1>

[eb]

PRELIMINARY186Hg on 107Ag1σ confidence levelno multiple Coulex

Coulex of 184,186,188Hg: Preliminary experimental results

Example: determination of the <2+||M(E2)||2+> matrix element in 186Hg.

0,8

1

1,2

1,4

1,6

1,8

2

-2 -1 0 1 2 3

<2+1||E2||2+

1> [eb]

<0+ g.

s.||E

2||2+ 1>

[eb]

PRELIMINARY186Hg on 107Ag1σ confidence levelno multiple Coulex

Coulex of 184,186,188Hg: Preliminary experimental results

Example: determination of the <2+||M(E2)||2+> matrix element in 186Hg.

0,8

1

1,2

1,4

1,6

1,8

2

-2 -1 0 1 2 3

<2+1||E2||2+

1> [eb]

<0+ g.

s.||E

2||2+ 1>

[eb]

PRELIMINARY186Hg on 107Ag1σ confidence levelno multiple Coulex

Coulex of 184,186,188Hg: Preliminary experimental results

Example: determination of the <2+||M(E2)||2+> matrix element in 186Hg.

0,8

1

1,2

1,4

1,6

1,8

2

-2 -1 0 1 2 3

<2+1||E2||2+

1> [eb]

<0+ g.

s.||E

2||2+ 1>

[eb]

Lifetime measurementD. Proetel et al., Phys. Lett. 48B, 102 (1974)

Coulex of 184,186,188Hg: Conclusion and outlook

Conclusions:

The heavy 184,186,188Hg were successfully produced and post-accelerated by REX-ISOLDE.

Apart from the first 2+ state, also other states have been populated.

The detected γ yields of the photo peaks can be used to extract:

• transitional matrix elements (B(E2) values)• diagonal matrix elements (quadrupole moments)

This is done by the program GOSIA by fitting the matrix elements to produce the obtained γ yields by a χ2

minimization. (T. Czosnyka et al, GOSIA2)

Coulex of 184,186,188Hg: Conclusion and outlook

Outlook:

A proposal for a Coulomb excitation experiment on 180,182Hg at REX-ISOLDE has been accepted.

A proposal for lifetime measurements in 184,186,188Hg at Argonne National Laboratory has been submitted.

Other experiments aiming at studying this heavy mass region have been proposed (Ra and Rn).

Coulex of 68Ni: Challenges and analysis improvements

π

82

2d5/21h11/2

2d3/23s1/2

1g7/2

1h9/2

ν

126

2f7/21i13/2

3p3/22f5/2

1h9/2

3p1/2

2g9/2

π

82

2d5/21h11/2

2d3/23s1/2

1g7/2

1h9/2

Me a

n S

quar

e C

harg

e ra

dii <

r2 >

• Influence of intruder states on the <r2> values in Pt and Hg isotopes• Evidence for a deviation of the <r2> values from the DM in Pb’s around 190-194Pb

0

500

1000

1500

2000

2500

3000

0+

2+

4+

6+

174 178 182 186 190 194Mass Number

E*[keV]

Hg (Z=80)

0p-2h

2p-4h

100 105 110 115 120 125 130

=0.1 fm2

Pb

Hg

Pt

N=104 N=126

Neutron Number

Pb 0+ & l.s.Pb 13/2+

Hg 0+ & l.s.Hg h.s.Pt g.s.Pt isomer

DM

0p-4h2p-6h

Mass Number

0+2+

4+

6+

8+

176 180 184 188 192 196

E*[keV] Pt (Z=78)

N=104

190Pb

oexistence and <r2> in the Lea

Coulex of 184,186,188Hg: Motivation

π=80

82

2d5/21h11/2

2d3/23s1/2

1g7/2

1h9/2

ν=106

126

2f7/21i13/2

3p3/22f5/2

1h9/2

3p1/2

2g9/2

0+2+

4+186Hg

0+

2+

4+

0

405

1080

523621808

Coulex of 184,186,188Hg: Motivation

π=80

82

2d5/21h11/2

2d3/23s1/2

1g7/2

1h9/2

ν=108

126

2f7/21i13/2

3p3/22f5/2

1h9/2

3p1/2

2g9/2

188Hg

0+

2+

4+

0+2+

4+

0

413

1005

824881

1208

Coulex of 184,186,188Hg: Preliminary experimental results

In August 2007 a Coulomb excitation experiment was performed on the neutron deficient 184,186,188Hg isotopes.

Doppler corrected γ spectrum

0+

2+

4+

0+2+

4+

0

413

1005

824881

1208Q>0

Q=0

Q<0

Q>0

Q=0

Q<0

Coulex of 184,186,188Hg: Preliminary experimental results

Coulex of 184,186,188Hg: Motivation

π=80

82

2d5/21h11/2

2d3/23s1/2

1g7/2

1h9/2

ν=104

126

2f7/21i13/2

3p3/22f5/2

1h9/2

3p1/2

2g9/2

184Hg

0+0

2+

4+

367

1089

6+1549

8+2057

shell model: π0p2h states

mean-field approximation:

slightly oblateJ.L.Wood et al, Phys, Rep., 215, 3&4 (1992)

Coulex of 184,186,188Hg: Motivation

π=80

82

2d5/21h11/2

2d3/23s1/2

1g7/2

1h9/2

ν=104

126

2f7/21i13/2

3p3/22f5/2

1h9/2

3p1/2

2g9/2

184Hg

0+0

2+

4+

367

1089

6+1549

8+2057

shell model: π4p6h states

mean-field approximation:

stronger prolatedeformation

0+375

2+4+

534653

6+994

8+1412

10+1901

J.L.Wood et al, Phys, Rep., 215, 3&4 (1992)

0+

2+

4+

0

367

1089

375

534653

0+

2+

4+

<18E0+E2

100

100 100