N = Z N=Z line coincides with doubly-magic core Single-particle states wrt 100 Sn core Neutron-proton correlations in identical orbitals Neutron-proton

N =

Z

N=Z line coincides with doubly-magic core

Single-particle states wrt 100Sn core

Neutron-proton correlations in identical orbitals

Neutron-proton (isoscalar) pairing

Emergence of collectivity...

Bo Cederwall AGATA Physics WS, Istanbul May 2010

LOI for the AGATA-PRESPEC campaign, GSI

Relativistic Coulomb excitation for probing special effectsRelativistic Coulomb excitation for probing special effectsof neutron-proton correlations around of neutron-proton correlations around 100100SnSn

B. CB. Cederwallederwall, R. Wadsworth, G. De France et al., R. Wadsworth, G. De France et al.

Main physics aimsMain physics aims

• Verify IsoscalarVerify Isoscalar spin-aligned neutron-proton couplingspin-aligned neutron-proton coupling schemescheme in in 92 92PdPd ( (9696Cd)Cd)

• Investigate Collective strength in Investigate Collective strength in 106,108 106,108Te,Te, 112112XeXe

by by measuring measuring B(E2; 0B(E2; 0++→ 2→ 2++))

Builds on our spectroscopic work at GANIL and JYFLBuilds on our spectroscopic work at GANIL and JYFL

and theoretical calculations by J. Blomqvist, R. Liotta, C. Qi, D. Delion et al.and theoretical calculations by J. Blomqvist, R. Liotta, C. Qi, D. Delion et al.


When approaching N=Z, ”normal” pair correlations may remain or evenbe extended:

Near N=Z we can have T=1T=1, I=0I=0 (”isovector”) nnnn, pppp Cooper pairsas well as npnp Cooper pairs (neutrons and protons occupy identical orbits)

and/or: T=0, I=1... (”isoscalar”) np pairing T=0, I=1... (”isoscalar”) np pairing

Does T=0 pairing exist and, if so, how should it best be revealed?

The nature of nuclear pair correlationsand their effect on nuclei near N=Z

So far, the search for T=0 np pairing has focused on special features: - g.s. binding energies of odd-odd nuclei - high-spin properties of N=Z nuclei (delayed alignments?) - deuteron transfer reactions


The isoscalar (np) pair gap is predicted toincrease sharply as NZ

Calculation by W. Satula, R. WyssPhys. Rev. Lett. Vol. 86, 4488 (2001)


• Shell model calculations by J. Blomqvist et al. predict strong T=0 neutron-proton (np) correlations leading to an isoscalar spin-aligned np coupling scheme for N=Z nuclei close to 100Sn.

An ”unexpected effect” of the NSM appearing in this exotic region of the nuclear chart

• Evidence for onset of collectivity, possibly induced by np pairing*) in neutron deficient Te and Xe nuclei

• The proposed experiments aim to confirm these theoretical predictions by measuring B(E2;0+ 2+) values.

*) M. Sandzelius, B. Hadinia, B. Cederwall, et al., Phys. Rev. Lett. 99, 022501 (2007).QRPA + np pairing calculations by D.S. Delion, R. Liotta et al. , PRC in press

“New” effects of neutron-proton correlations around 100Sn


What is the g.s. structure of N=Z nuclei below What is the g.s. structure of N=Z nuclei below 100100Sn?Sn?

The conventional picture :The conventional picture :

ΨΨ=({νg =({νg 9/29/2-2-2}}0+0+))nn x ({πg x ({πg 9/29/2

-2-2}}0+0+))nn

This would lead to a normal seniority type spectrum of This would lead to a normal seniority type spectrum of low-lying excited stateslow-lying excited states

νg9/2-1

νg9/2-1

πg9/2-1

πg9/2-1

νg 9/2-1 νg 9/2

-1

πg9/2-1

πg9/2-1

100Sn

9292PdPd

For For 9292Pd and Pd and 9696Cd Cd neutrons and protonsneutrons and protonsmainly occupy the mainly occupy the g g 9/29/2 subshellsubshell

νg9/2-1

νg9/2-1

πg 9/2-1

πg 9/2-1

100Sn

9696CdCd


Shell Model calculations predict strong np interactionsShell Model calculations predict strong np interactions Transition to new spin-aligned T=0 np coupling scheme Transition to new spin-aligned T=0 np coupling scheme

for N=Z nuclei below for N=Z nuclei below 100100Sn (J. Blomqvist et al.)Sn (J. Blomqvist et al.)

ΨΨ=[({νg =[({νg 9/29/2-1 -1 xx πg πg 9/29/2

-1-1}}9+9+))22]]0+0+

x x [({νg [({νg 9/29/2-1 -1 xx πg πg 9/29/2

-1-1}}7+7+))22]]0+ 0+

100Sn

πg9/2-1 νg9/2

-1

νg9/2-1 πg9/2

-1

πg9/2-1νg9/2

-1

νg9/2-1

πg9/2-1

Model space: g9/2 (and f5/2 , p3/2 ,p½ )9292PdPd

Aligned np coupling:Aligned np coupling:

100Sn

πg9/2-1

νg9/2-1

νg9/2-1

πg9/2-1

9696CdCd

ΨΨ=[({νg =[({νg 9/29/2-1 -1 xx πg πg 9/29/2

-1-1}}9+9+))22]]0+0+


Pd level systematics near N=ZPd level systematics near N=Z

Shell model calculations by J. Blomqvist, R. Liotta, C. Qi

92Pd, theory 92Pd, exp 94Pd, exp94Pd, theory 96Pd, theory 96Pd, exp


Pd level systematics near N=ZPd level systematics near N=Z- effects of np interactions- effects of np interactions



New manifestation of T=0 np ”pairing”? New manifestation of T=0 np ”pairing”?

100Sn

l=6 l=6

l=8l=8

9292PdPd

Special deuteron-hole cluster like ground states imply significant deformation

”Nuclear belly dancers”

100Sn

l=8

l=8

9696CdCd


B(E2; 0B(E2; 0++ 2 2++) – sensitive probe of neutron-proton interactions) – sensitive probe of neutron-proton interactions

Bo Cederwall AGATA Physics WS, Istanbul May 2010 Shell model calculations by J. Blomqvist, R. Liotta, C. Qi

Enhanced collective strength at N=Z


Evidence for enhanced collectiveEvidence for enhanced collectivestrength in Te and Xe nuclei approaching N=Zstrength in Te and Xe nuclei approaching N=Z

TZ=1 nucleus 106Te : B. Hadinia, B. Cederwall et al., Phys. Rev. C 72, 041303 (2005)


Te experimental E(2+) and B(E2; 2+→ 0+)

TZ=1 nucleus 110Xe; M. Sandzelius, B. Hadinia,, B. Cederwall et al., Phys. Rev. Lett. 99, 022501 (2007)


Xe experimental E(2+) and B(E2; 2+→ 0+)

Taken from R.F. Casten, 2003 Taken from R.F. Casten, 2003

These trends can change with np pairing as N→Z !Enhancement of collectivity due to np (short-range) pairingcorrelations predicted in new calculations by D.S Delion, R. Liotta et al.

Quadrupole collectivityQuadrupole collectivityThe traditional view of the mechanism behind deformation and collectivity: long range np QQ

interactions


New QRPA + np pairing calculations predict New QRPA + np pairing calculations predict enhanced collectivity near the N=Z=50 double shell enhanced collectivity near the N=Z=50 double shell

closure induced by np pairing correlations (D.S. closure induced by np pairing correlations (D.S. Delion, R. Liotta Delion, R. Liotta et alet al.).)

p-h excitationsinduced by np pairing

Strong decrease in E(2+)with increasing Δpn

Much smaller effectfrom long-range QQ np int.


Shell model calculations for light Te isotopes indicate Shell model calculations for light Te isotopes indicate that configuration mixing due to the monopole that configuration mixing due to the monopole

tensor tensor force between primarily the proton 0gforce between primarily the proton 0g7/27/2 and and neutron 1dneutron 1d5/25/2 orbitals orbitals can induce enhanced can induce enhanced

collectivity (C. Qi, R. Liotta collectivity (C. Qi, R. Liotta et alet al.).)


Octupole deformation and correlations near N=Z

34

56

88

134

202

56112

56 Ba

“Doubly-magic octupole-deformed”nucleus predicted by theory

Strong octupole correlations are expectedin nuclei where normal-parity single-particlestates and intruder states differing byΔl = Δj = 3 are near the Fermi surface.

Coherent octupole correlations forneutrons and protons should occurnear N=Z.

Can we observe additional enhancementdue to dynamic np correlations ?

Next to 112Ba (accessible with current technology?) 110Xe56 and 109I56 might have the largest octupole stability.

Enhanced octupole correlations in light Te-Xe nuclei

J.F. Smith et al.Phys. Lett B523, 13 (2001) (Gammasphere)

G. de Angelis et al.Phys. Lett B535, 153 (2002) (Euroball)

G.F. Lane et al.Phys. Rev. C57, R1022 (1998) (Gammasphere)


• Measure B(E2; 0Measure B(E2; 0++22++) for isotopic chain ) for isotopic chain 92,94,9692,94,96PdPd (from N=Z to N=50 closed shell)(from N=Z to N=50 closed shell)

• Measure E(2Measure E(2++) for ) for 9696Cd and B(E2; 0Cd and B(E2; 0++22++) for ) for 96,9896,98CdCd (from N=Z to N=50 closed shell) (from N=Z to N=50 closed shell)

• Search for decay of 16Search for decay of 16++ spin trap isomer for spin trap isomer for 9696CdCd

Confirm spin-aligned neutron-proton coupling scheme andcharacterize np interactions (T=0/T=1)

• Measure E(2Measure E(2++) for ) for 106106Te and B(E2; 0Te and B(E2; 0++22++) for ) for 106,108106,108Te, Te, 112112XeXe

Measure and characterize collective strength

Proposed ExperimentsProposed Experiments


Experimental detailsExperimental details

Projectile fragmentation FRS – AGATA – LYCCAProjectile fragmentation FRS – AGATA – LYCCA92-9692-96Pd: LISE++ calc for primary beam Pd: LISE++ calc for primary beam 106106CdCd

Ebeam = 650 MeV/u Ibeam = 1 pnA

S4 ion and γγ-ion ratesSetting 1: optimizing for 92PdSetting 2: optimizing for 94PdAssume 15% AGATA pp efficiency, σ(Coulex) from DWEIKO


Setting 92Pd 94Pd 96Pd

S4(s-1)

γ-ion (per day)

S4(s-1)

γ-ion (per day)

S4(s-1)

γ-ion (per day)

1 1.6 200 8.0 1000 - -

2 - - 1000 1.2·105 300 3.8·104

Experimental details, ct’dExperimental details, ct’d

Projectile fragmentation FRS – AGATA – LYCCAProjectile fragmentation FRS – AGATA – LYCCA96-9896-98Cd: LISE++ calc for primary beam Cd: LISE++ calc for primary beam 112112SnSn


S4 ion and γγ-ion ratesSetting optimized for 96Cd

Assume 15% AGATA pp efficiency, σ(Coulex) from DWEIKO


96Cd 98Cd

S4(s-1)

γ-ion (per day)

S4(s-1)

γ-ion (per day)

0.1 13 4.0 500

Experimental details, ctd’Experimental details, ctd’

Projectile fragmentation FRS – AGATA – LYCCAProjectile fragmentation FRS – AGATA – LYCCA106,108106,108Te, Te, 112,114112,114Xe : LISE++ calc for primary beam Xe : LISE++ calc for primary beam 144144SmSm


S4 ion and γγ-ion ratesSetting 1: optimizing for 106Te

Setting 2: optimizing for 112XeAssume 15% AGATA pp efficiency, σ(Coulex) from DWEIKO


Setting 106Te 108Te 112Xe 114Xe

S4(s-1)

γ-ion (per day)

S4(s-1)

γ-ion (per day)

S4(s-1)

γ-ion (per day)

S4(s-1)

γ-ion (per day)

1 0.2 25 20 2.4·103 - - -

2 - - - - 30 3.6·103 1.0·103 1.2·105

Backup slidesBackup slides


9292Pd analysis (prel) Pd analysis (prel) γγγγ2n2n

Three Three γγ rays firmly identified, mutually concident rays firmly identified, mutually concident

γ -gated on 2+- 0+

γ -gated on 6+- 4+

6+- 4+

2+- 0+4+- 2+

4+- 2+


92.94,9692.94,96Pd levels and the role of T=0 np interactions at N=Z Pd levels and the role of T=0 np interactions at N=Z


92Pd theofull np

92Pd theono np

92Pd T=0

92Pd T=1

96Pd theo

96Pd exp

96,9896,98CdCd

Shell model calculations by . Blomqvist, R. Liotta, C. Qi et al.


Pd level systematics near N=ZPd level systematics near N=Z



96,9896,98Cd level and the role of T=0 np interactions at N=Z Cd level and the role of T=0 np interactions at N=Z

96Cd theofull np

96Cd theono np

96Cd T=0

96Cd T=1

98Cd theo 98Cd


Documents

N = Z N=Z line coincides with doubly-magic core Single-particle states wrt 100 Sn core Neutron-proton correlations in identical orbitals Neutron-proton