Coulomb Excitation of Neutron-rich Isotopes

around A~140(IS 411)

Thomas Behrens

Physik-Department E12

TU München

Physical motivation:Evolution of B(E2) values around N=82

Experimental setup and realisationat REX-ISOLDE with MINIBALL

Preliminary resultsfor 144Xe & 124,126Cd

Conclusion & Outlook

Isospin dependent modification of Grodzins’ rule

Modified Grodzins’ rule

)(088.0288.157.2

]b)[20;2(]keV)[2(3/22

2211

NNAZ

eEBE gs

3/2

3/2

064.00.1

0128.00.1

2 A

AAN

Minimum mass for fixed A (from Weizsäcker’s mass formula)

Grodzins’ rule (version by Raman)3/2222

11 57.2]b)[20;2(]keV)[2( AZeEBE gsMotivationMotivation

SetupSetup

ResultsResults

OutlookOutlook

[S.Raman et.al., Atomic Data and Nucl. Data Tables 78,1 (2001)]

[D.Habs, R.Krücken, INTC-P-156 (2002)]

B(E2) values before IS411

MotivationMotivation

SetupSetup

ResultsResults

OutlookOutlook

136Te

122Cd

140Xe ?

B(E2) values after 2004

MotivationMotivation

SetupSetup

ResultsResults

OutlookOutlook

122,124Cd

140Xe

preliminary results:

122Cd: 0.37(11) e2b2

124Cd: 0.32(10) e2b2

136Te

B(E2) values after 2005

MotivationMotivation

SetupSetup

ResultsResults

OutlookOutlook

138,140,142Xe

preliminary results:

138Xe: 0.38(2) e2b2

140Xe: 0.52(2) e2b2

142Xe: 0.69(2) e2b2

136Te

Coulomb Excitation

b

Target Z

Projectile • Beam energy below Coulomb barrier “Safe Coulex”

• proj ~ 0.06 c (Doppler correction)

CE i

f

2)2(

12

1)2( if

i

JEMJJ

EB

)(

)(

)(

)(

)(

)(

)(

)(64

126

126

64

126

64

64

126

ZnN

CdN

CdW

ZnW

Cd

Zn

Zn

Cd

CE

CE

MotivationMotivation

SetupSetup

ResultsResults

OutlookOutlook

REX-ISOLDE & MINIBALL

MINIBALL

MotivationMotivation

SetupSetup

ResultsResults

OutlookOutlook

REX-ISOLDE

MINIBALL

124,126Cd(Laser Ionization)

144Xe

Experimental Setup

Gamma-spectroscopy

MINIBALL

Particles• Angles• Energies

DSSSD

Univ. of Edinburgh

Beammonitor

PPAC

TU Darmstadt

Target

Beam

Beampurity

Beam DumpDetector

MotivationMotivation

SetupSetup

ResultsResults

OutlookOutlook

Statistics for Cd isotopes

• Protons on converter target (didn’t hit the converter!)• new quartz transfer line improved purity!!• Laser ionization (RILIS)• varying beam intensities and purities (increasing In) problems with the ISOLDE target• tried different settings for line heating and target heating

MotivationMotivation

SetupSetup

ResultsResults

OutlookOutlook

Isotop Target[mg/cm2]

Laser ON [h]

Laser ON/OFF [h]

E from REX[MeV/A]

beam intensity [104 pps]

beam purity [%]

124Cd 64Zn[1.8]

15 6.5 2.85 0.9 - 1.5 40 - 85

126Cd 64Zn[1.8]

26 7 2.85 1.4 75

Statistics for Xe isotopes

• shielding to slow down ejectiles at low lab

changed due to low energy from REX • changed target to check for scattered particles beam was not focused, might have hit collimator• changes of IH phase, line & target heating improved intensity• 2h on stopper foil looking for decay lines of 144Cs

MotivationMotivation

SetupSetup

ResultsResults

OutlookOutlook

Isotop Target[mg/cm2]

Shield [mg/cm2]

Running time [h]

E from REX[MeV/A]

beam intensity [104 pps]

beam purity [%]

144Xe 96Mo [1.7]

Al foil[4.1]

2.5 2.55 ~5.4 ~90

144Xe 197Au [1.0]

Al foil[1.5]

1 2.55 ~5.4 ~90

144Xe 96Mo [1.7]

My foil[1.6]

19 2.7 ~5.4 ~90

CD energy vs angle

MotivationMotivation

SetupSetup

ResultsResults

OutlookOutlook

64Zn

124Cd

Ep

art

[a.

u .]

MotivationMotivation

SetupSetup

ResultsResults

OutlookOutlook

124Cd: E(21+) peaks

124CdFWHM ~12 keV

64ZnFWHM ~14 keV

runnig time: ~15 h (Laser ON)

Doppler correction incl. particle reconstruction

Contaminants: 124In, 124Cs

126Cd: E(21+) peaks

MotivationMotivation

SetupSetup

ResultsResults

OutlookOutlook

126CdFWHM ~15 keV

64ZnFWHM ~15 keV

runnig time: ~26 h (Laser ON)

Doppler correction incl. particle reconstruction

Contaminants: 126In, 126Cs

144Xe: E(21+) peaks

MotivationMotivation

SetupSetup

ResultsResults

OutlookOutlook

144XeFWHM ~6 keV

96Mo~25 counts

runnig time: ~19 h (2.7 MeV/A)

Reconstruction of Recoils for Doppler correction

elastic scattered Xe to be used for normalization

B(E2) values after 2006

MotivationMotivation

SetupSetup

ResultsResults

OutlookOutlook

Preliminary Results:

Isotope B(E2)[e2b2]

124Cd 0.35(6)

126Cd 0.22(3)

144Xe 0.73(18)

144Xe126Cd

136Te

Conclusion & Outlook

MotivationMotivation

SetupSetup

ResultsResults

OutlookOutlook

successful measurement of 144Xe & 124,126Cd no derivation from systematic

open tasks:• beam contamination• CD efficiency• angular distribution of ’s• 144Xe: normalize to Rutherford

proposed:• development of BaF+ beams for Ba isotopes• 128Cd is feasible

Future Experiments

MotivationMotivation

SetupSetup

ResultsResults

OutlookOutlook

Mass Number

Ba isotopes

140Ba 148Ba

dashed line: theoretical calculation[N.Shimizu et.al., Phys.Rev.Lett. 86,1171 (2001)]

solid line: modified Grodzins` rule [S.Raman et.al., Atomic Data and Nucl. Data Tables 78,1 (2001)]

150Ba ?

Helping hands and heads...

T. Behrens1, V. Bildstein1, R. Gernhäuser1, Th. Kröll1,R. Krücken1, M. Mahgoub1, P. Maierbeck1, W. Weinzierl1,

D. Habs2, R. Lutter2, T. Morgan2, P. Thirolf2, F. Finke3, M. Seidlitz3, N. Warr3, D. Weisshaar3,

S. Franchoo4, J. Diriken5, P. van Duppen5, O. Ivanov5, I. Stefanescu5,

J. van de Walle5,6, J. Cederkall6, L. Fraile6, U. Köster6, T. Sieber6, D. Voulot6, F. Wenander6,

A. Ekström7, T. Davinson8,and the REX-MINIBALL collaboration

1TU München, 2LMU München, 3Universität zu Köln, 4IPN Orsay, 5KU Leuven, 6CERN,

7Lund University, 8University of Edinburgh,

Thank you for your attention!

REX-ISOLDE @ CERN

0 5 10 m

ISOLDE

NEW:NEW:

3 MeV/A

Targets

Thomas Behrens

MINIBALL

IS411 – Intensity on CD

MotivationMotivation

SetupSetup

ResultsResults

OutlookOutlook 96Mo(144Xe,144Xe)96Mo:

Beam shift: ~2 mm

Hits on CD in polar coordinates

x [mm]

y [m

m]

Physical MotivationEmpirical relation between E(2+) and B(E2) [Grodzins’ Rule]

B(E

2) e

xp /

B(E

2) th

eo

NN

B(E2) smaller than expected

(N.V. Zamfir et.al., Phys.Rev.C 51 (1995) 98 )

Modified version (Habs, Krücken, INTC-P-156 (2002) )

)(088.0288.1(*57.2

)2()2(3/22

1

NNAZ

EBE