Spectroscopy studies by decay

-Proton-rich nuclei N~ZDeformation in the mass region A~75Fundamental aspects of weak interaction, test of CVC

-Neutron-rich nuclei Z~20effective interaction in the mass region A~50

Cécile Jollet, IReS Strasbourg, TAS Workshop, Caen March 31, 2004

decay: general features

Exploration of nuclei with large Q value (nuclei far from stability) Provides the first information on new speciesFundamental aspects of weak interaction

Nuclear structureNucleosynthesis

Spectroscopy detection of , and delayed particules (neutrons or protons, and -rays)

Informations provided: Mass excessHalf-life T1/2

feedings Ift = f(Z,Q-Ex) T1/2 / Ift = Cste / |Mif|2

Matrix elements, nuclear configurations

1-Proton-rich nuclei N~Z, A~75

Theoretical and experimental works in this region shape isomerism or shape coexistence strongly deformed ground states

Good efficiency for detection on the whole QEC window construction of a new Total Absorption gamma Spectrometer (TAgS)

Installation of TAgS at ISOLDE in 2001

Study by decay: 72,73,74,75Kr and 76,77,78Sr

Detection: TAgS + Ge detectors (X, ) and plastic scintillators ()

In this region, large part of the GTGR is accessible by decay Estimate the deformation by measuring the complete B(GT)

distribution

Hamamoto, Sarriguren Shape of the GT strength distribution depends on the shape of parent nucleus ground state

I. Hamamoto et X. Z. Zhang, Z. Phys. A353 (1995) 145.

Total Absorption gamma Spectrometer (TAgS) (Madrid, Strasbourg, Surrey, Valence)

NaI monocrystal (diameter=38cm, length=38cm)

+8 PMTs 5”

Ancillary X, , detectors

TAgS properties:Energy resolution: 7.1% at 662 keV

5.4% at 1332 keV

Efficiency at 662 keV: 95(8)% total 83(7)% photopeak

Solid Angle: 97% of 4

Boron polyethylene:10cmLead:5cmCopper:2cmAluminium:2cm

Shielding

Collection point

New beam line

Tape transportsystem

1-Proton-rich nuclei N~Z, A~75

76Sr --------> 76Rb+ EC

E. Nácher et al., submitted to PRLE. Poirier et al., PRC69,034307 (2004)

74Kr --------> 74Br+ EC

Shape mixing Prolate shape

Results in good agreement with theory and with previous experiments decay studies value and sign of the deformation

validation of TAgS spectroscopy

oblate

prolateexp.

1- Proton-rich nuclei N~ZFundamental aspect of weak interaction

V-A theory, hyp: the Vector Current is conserved (CVC)vector part of weak interaction not influenced by strong interaction

To test CVC: study of superallowed Fermi transitions 0+0+ Ft = ft (1+r) (1-c) = cste (r, c are correction terms)

We need to determine the complete decay scheme, r and c

TAgS measure branching ratios and T1/2 with the required precision

Current measurement with TAgS : study of 62Ga

for A=10-54, Ft=3072.3(2.0) s with precisions: 3.10-4 for T1/2

3.10-4 for branching ratios 5.10-5 for energy

In progress, new measurements for A>54

Ft

(s)

62Ga

66As

70Br

74Rb

88Y

82Nb

86Tc

Z

Ft

(s)

3065

3070

308010C

14O

26Al

34Cl

38K

42Sc

46V

50Mn54Co

Present results

g 9/2

2-Neutron-rich nucleiA~50, Z~20

(F. Perrot thesis)

Neutron-rich nuclei large Q-Sn energy windowWe need efficient neutron and gamma detection direct knowledge of I, Pxn and Ex

Allowed GT transitions non natural parity states

d3/2

f7/2

p3/2

p1/2

f5/2

x x x x

x

52K3319

x x x

x

52Ca3220

xfp shell

sd shell

Ex>4 MeV (above Sn)

p-n interaction across sd-fp shell

forbidden GT transitions natural parity states

d3/2

f7/2

p3/2

p1/2

f5/2

x x x x

x

52K3319

x x x

x

52Ca3220

x

n-n interaction across fp shell

Non nat

51, 52, 53 K(1/2,3/2+) (2-) (3/2+)

51, 52, 53 Ca(3/2-) (0+) (3/2-)

allowed

forbiddenGT

gs

Q~14-16 MeV

Sn~3.5-4.5 MeV

delayed neutrons

nat

TONNERRE Detector(LPC Caen, IFIN Bucarest)

En= 0.2-7 MeV ~ 11% at 1 MeV

Low energy neutron detectors (x8)(IReS)

En = 0.05-3.0 MeV ~ 0.5% at 1 MeV

Ge Clusters (x2) (MINIBALL collaboration)

~ 5% at 1.3 MeV and 4 (start n-TOF)

~ 70%

2-Neutron-rich nucleiA~50, Z~20

Experimental setup at ISOLDE

In red: new transitionsIn green: new neutron emitter states and transitions

52K decay detection of both low and high energy neutrons53K decay only part of the statistics

Comparison with theory for 51,52,53Ca in progress (E. Caurier, F. Nowacki, IReS)

2-Neutron-rich nucleiA~50, Z~20 Preliminary results

52K --------> 52Ca-

53K --------> 53Ca-

Conclusions & Perspectives

High efficiencystudy of N~Z nuclei deformation A~80 CVC test 74Rb … mirror decays 71Kr, 75Sr

We have 2 experimental setup which are performing to explore the nuclear structure:

TAgS LEND-TONNERRE coupling

Efficient neutron detectionEffective interaction, shell orderNeutron-rich nuclei near the closed shell35,36Al, Cu, Zn…

Such investigations can be performed using any low energy beamsat ISOLDE, Ganil, Alto…

Nuclei A at/s

ISOLDE

Kr 71

72

73

74

75

3.5

3.103

5.105

2.106

1.8.107

Sr 75

76

77

78

5

4.103

2.105

9.2.105

Rb 74 2.103

Ga 62 400

Nuclei A at/s

ISOLDE

at/s

ALTO

K 49

50

51

52

53

5.4.105

7.4.104

9.103

1.2.103

4

Na 33

3440

2

Al 34

352.6

8

Ni 69

704.104

2.104

2.104

1.104

Cu 76

77

78

79

4.104

4.103

4.102

1

2.104

2.103

2.102

Zn 76

78

80

3.2.107

2.106

2.104

5.9.105

2.105

2.104

Sn 128-132

133

134

135

136

137

4 - 6.108

3.107

4.106

2.105

6.103

2.102

1.2.106

at/s

SPIRAL

2.102

3-6.103

1.5.104

4.105

Production yield information

ISOLDE : http://isolde.web.cern.ch/isolde/ Ulli Koster

SPIRAL: http://www.ganil.fr/operation/available_beams/radioactive_beams.htm

ALTO: Fadi Ibrahim (preliminary estimation)

Collaboration

A. Algora J.C. Angélique G. Ban P. Baumann F. Benrachi C. Borcea

M.J.G. Borge A. Buta D. Cano-Ott J.C Caspar E. Caurier S. Courtin

P. Dessagne J. Devin D. Etasse L.M. Fraile F. Perrot W. Gelletly S. Grévy G. Heitz C. Jollet A. Jungclaus F.R. Lecolley E. Liénard G. Le Scornet

F. Maréchal C.Miéhé E. Nacher F. Negoita F. Nowacki N. Orr E. Poirier

M. Ramdhane B. Rubio M.D. Salsac P. Sarriguren J.L. Tain O. Tengblad

C. Weber

The IReS workshop and the ISOLDE Collaboration

Neutrons transmission

Efficiency of neutrons detector : Tonnerre, LEND