nuclear moments of isomeric states studied in transfer reactions in inverse kinematics

D.L. Balabanski EURISOL workshop, Florence, 16.01.2008

1

Nuclear moments of isomeric states studied in

transfer reactions in inverse kinematics

• moments of exotic isomers: where are we now and what we want to do in near future


2

Nuclear moment measurements

magnetic moment () quadrupole moment (Q)

single-particle configuration (configuration mixing)

collective properties(deformation, effective charges)

Spin-orientedbeams


3

''

mmfor

pp mm

polarizationalignment

prolate oblateisotropic

','

mmfor

pp mm

'

'

mmfor

pp mm

- decay – ray detection

Spin orientation


4

A

k

kks

A

k

kk sgg1

)()(

1

)()(l l

Magnetic moment

= g I N

= <I, m=I | z | I,m=I>

Quadrupole moment

2 2(3. )i i ii

e z r = 2

2 ( , )i i i ii

e r Y .

Q = 02, ,I m I I m I Q

Q(j) =

22 1

2( 1)j j

je r

j

what we want to measure


5

how are done these measurements


6

B

JFragment beam

METHODOLOGY

L = -gNB/h

Measure Larmor precesionand decay I(t)

Time Differential Perturbed Angular Distribution

t=0 time

Field UPField DOWN

2L

2A2B2

the relative phases depend on the g-factor

time

1 2

1 2

( )I I

R tI I

detectors at ±45° and ±135°detectors at ±45° and ±135°


7

Fusion-evaporation reaction

basic tool for obtaining of spin-aligned nuclei in the past two-three decades

fragmentation reaction

the present tool :

- 20 % spin-polarization (low yield)

- 10 ÷ 30 % spin-alignment (high yield)

where are we now


8

ALIG

NM

EN

T(%

)

+6.2(7)%

GENERAL ASPECTS of g-factor measurements with fast beams

4. FEASIBILITY: SPIN-ALIGNMENT !

PROJECTILE FRAGMENTATION +

selection in longitudinal momentum(slits in FRS or via ion-correlation) CONDITION:

STRIPPED FRAGMENTS !61FeYIELD

61Fe

-15.9(8)%

61Fe

61Fe


9

Higher spins for greater A.

M. Pfützner et al., Phys. Rev. C65 (2002) 064604; K. Gladnishki et al., Phys. Rev. C69 (2004) 024617


10

gexp. (61mFe) = - 0.229(2)

I. Matea et al. PRL 93 (2004) 142503

Experiments at GANIL at intermediate energies(credits to Micha Hass, Jean-Michel Daugas, Georgi Georgiev,

Gerda Neyens, Iolanda Matea and Nele Vermuelen)

G. Georgiev, JP G 28 (2002) 2993


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201 keV M1 transition 654 keV M2 transition

Q(61mFe; g9/2) = 422(60) mb

Quadrupole moments: 61Fe test case 61Feexp. July 2005

principle investigators: Micha Hass (Rehovot) and Jean-Michel Daugas (Bruyeres-la-Chatel)


12

THE EXPERIMENTAL SET-UP AT GSI: g-RISING

Spin-aligned secondary beam selected(S2 slits + position selection in SC21)

SC41 gives t=0 signal for -decay time measurement

Implantation: plexiglass degrader + 2 mm Cu (annealed)

SC42 and SC43 validates the event


13

The 136Xe fragmentation experiment

Z

A/q

127Sn

analysis:L.Atanasova, Sofia


14

E2E2

E1E1M2M2

1095 keV

715 keV

??


15

1095 keV

715 keV

FFT

TDPAD

715 keV


16

classical view quantum-mechanical view

Pop

ula

tion

I = 2

E

m =2m =1

m =0m =-1

m =-2

I=2 ensemble

Necessary to induce polarization of the beam prior the measurement

ISOL beams


17

The 63m,65mNi experiment (I = 9/2+)

(d,p) reactions

Tandem at IPN-Orsay

• pulsed 6 MeV 1 nA D beam

• enriched 64Ni/62Ni (ferromagnetic)

targets

• known g(63mNi) = - 0.269(3)Muller et al. PR B40, 7633 (1989)

• HF field of Ni(Ni) = 6.90(5) TRiedi et al. PR B15, 5197 (1977)

Part II: The future: Transfer reactions with RIBs


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63mNi 65mNi

gexp. = -0.296 (3)

G. Georgiev et al, J.Phys.(London) G31, S1439 (2005)

Ni exp.2004

Bg N

L

Larmor frequency

)}(2cos{4

3

),2(),(

),2(),()(

22

22

tBA

BA

tItI

tItItR L

HF field Ni(Ni) = 6.90(2) T

Experimental results

~ 15% alignment in transfer reactions at the Coulomb barrier (3 MeV/u)

Part II: The future: Transfer reactions with RIBs


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inverse kinematics63Cu beam @ 220 MeV (3.5 MeV/u)

CD2 target (2 mg/cm2)

Ni ferromagnetic backing (15 µm)

permanent magnet for holding fieldParticle identification: Si strip detector (8 annular strips) as ECsI 16 sectors – as E detector angular coverage 25° - 60°

ADWA (d,p) calculations for 3.5 MeV/u 63Cu beams

0.00

0.10

0.20

0.30

0.40

0.50

0.60

10 40 70 100 130laboratory angle (degrees)

mb/sr

cu64 6- isomer 3.76 mb


20


21

The CD detector of TIARA

The CsI detector

Particle detection with TIARA(in collaboration with Surrey, Birmingham)


22


23


24

orientation in transfer• Single-nucleon transfer (d,p)

– 65Ni• B2 = 0.159(5)

– 66Cu• B2 = 0.452(13)

– 64Cu• “standard” B2 = 0.09 (?)

• with p- coincidences B2 > 0.27

• Multi-nucleon transferstates with higher spin become accessible (!)


25

Towards the use of ISOL beams• With radioactive beams the reaction products should be stopped in the

target (isomeric state) while the beam should be let go through – very fine control of the target thickness needed

• Single-nucleon transfer:

very clean experimental conditions (very few reaction channels opened)

reasonable orientation from the reaction

mostly single-particle states accessible

very difficult separation of the beam/reaction products

• Multi-nucleon transfer:

many more reaction channels opened

orientation higher than in single-nucleon transfer

multi quasi-particle states accessible as well

the separation of the beam/reaction products should be easier


26

64Cu – target problemsA CD2 target of ~2 mg/cm2 dose not stand ~0.3 enA (17+) 63Cu beam (~1E8 pps) for more than 20 hours (~7E12 p)

The effect is DOSE and not HEAT related!


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Targets: Hydrogen (Deuterium) storage

T. Yildirim et al. PR B72, 153403 (2005)


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collaboration (or in other words) who is doing the job

GANIL experiments• Jean-Michel Daugas, Micha Hass, …GSI experiments • Gerda Neyens, Gary Simpson, Adam Maj, Micha Hass, DLBTransfer reactions• Georgi Georgiev and DLB

+ few (but good!) students and post-docs who really do the job!


29

s isomers in the Sn regionNN=82=82

1g7/2

1h11/2

3s1/2

2d3/2

2d5/2

NN=50=50

J. Pinston et al, PRC61 024312 (2000) , J. Pinston et al, JPG30 (2004) R57,NNDC data base and this work

d3/2-1h11/2

-1

Odd Sn

Even Sn

d3/2-1h11/2

-2

h11/2 -d3/2

-1h11/2 -1

d3/2-1h11/2

-2

h11/2 x 5- core h11/2 x 7- core

h11/2 -

h11/2

s1/2-1

d3/2-2

Brown et al, PRC71 (2005) 044317

Newly identifiedisomers


30

Structure of the 19/2+ isomer in 127Sn

• the spin-parity assignment of the 19/2+ isomer is based on energy systematics J. Pinston et al., PRC 61, 024312 (2000)

• suggested configuration: (ννh11/2 1 5)19/2+; gexp(h11/2) = 0.24

• the 5 isomers in even-even Sn isotopes take experimental values: gexp(5) 0.06 and are understood as an admixture of (ννh11/2

1d3/2 1)5- with gemp = 0.26

(ννh11/2 1s1/2

1)5- with gemp = 0.09

• for the structure of the 19/2+ isomer an admixture with the νg7/2 1h11/2

2 configuration is

suggested in order to explain the l -forbidden M2 isomer-decay transition.

gemp(νs1/2 1 h11/2

2) = 0.15 gemp(νg7/2

1 h11/2 2) = 0.23

• the fragmentation g-RISING experiment yields gexp 0.16

• LSSM calculations yield gSM = 0.21 (calculation M.Hjorth-Jensen)

nuclear moments of isomeric states studied in transfer reactions in inverse kinematics

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