Spectroscopy studies by  decay Proton-rich nuclei N~Z Deformation in the mass region A~75

1. Spectroscopy studies by  decay • Proton-rich nuclei N~Z • Deformation in the mass region A~75 • Fundamental aspects of weak interaction, test of CVC • Neutron-rich nuclei Z~20 • effective interaction in the mass region A~50 Cécile Jollet, IReS Strasbourg, TAS Workshop, Caen March 31, 2004

2. Nuclear structure Nucleosynthesis Exploration of nuclei with large Q value (nuclei far from stability)  Provides the first information on new species Fundamental aspects of weak interaction  decay: general features Spectroscopy detection of, and delayed particules (neutrons or protons, and -rays) Informations provided: Mass excess Half-life T1/2  feedings I ft = f(Z,Q-Ex) T1/2 / I ft = Cste / |Mif|2  Matrix elements, nuclear configurations

3. 1-Proton-rich nuclei N~Z, A~75 Theoretical and experimental works in this region  shape isomerism or shape coexistence  strongly deformed ground states Hamamoto, Sarriguren  Shape of the GT strength distribution depends on the shape of parent nucleus ground state • In this region, large part of the GTGR is accessible by  decay • Estimate the deformation by measuring the complete B(GT) distribution 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 () I. Hamamoto et X. Z. Zhang, Z. Phys. A353 (1995) 145.

4. Boron polyethylene:10cm Lead:5cm Copper:2cm Aluminium:2cm Shielding Ancillary X, ,  detectors Collection point Tape transport system Total Absorption gamma Spectrometer (TAgS) (Madrid,Strasbourg, Surrey, Valence) NaI monocrystal(diameter=38cm, length=38cm) +8 PMTs 5” 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 New beam line

5. b+ EC b+ EC 74Kr --------> 74Br 76Sr --------> 76Rb oblate prolate exp. 1-Proton-rich nuclei N~Z, A~75 E. Poirier et al., PRC69,034307 (2004) E. Nácher et al., submitted to PRL 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

6. Present results 42Sc 3080 • for A=10-54, Ft=3072.3(2.0) s • with precisions: 3.10-4 for T1/2 • 3.10-4for branching ratios • 5.10-5for energy • In progress, new measurements for A>54 66As 10C Ft (s) 50Mn Ft (s) 86Tc 54Co 70Br 38K 82Nb 26Al 46V 3070 88Y 34Cl 14O 3065 Z 62Ga 74Rb g 9/2  1- Proton-rich nuclei N~Z Fundamental 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

7. (F. Perrot thesis) 51, 52, 53 K (1/2,3/2+) (2-) (3/2+) allowed Q~14-16 MeV delayed neutrons forbidden GT Sn~3.5-4.5 MeV nat gs 51, 52, 53 Ca (3/2-) (0+) (3/2-) Allowed GT transitions  non natural parity states forbidden GT transitions  natural parity states Ex>4 MeV (above Sn) f5/2 f5/2 x x x x p1/2 p1/2 fp shell x x x x xx x x x x x x x x x p3/2 p3/2 f7/2 f7/2 d3/2 d3/2 x sd shell         52K33 52K33 52Ca32 52Ca32 p-n interaction across sd-fp shell n-n interaction across fp shell 20 19 20 19 2-Neutron-rich nuclei A~50, Z~20 Neutron-rich nuclei  large Q-Sn energy window We need efficient neutron and gamma detection  direct knowledge of I, Pxn and Ex Non nat  

8. 2-Neutron-rich nuclei A~50, Z~20 TONNERRE Detector (LPC Caen, IFIN Bucarest) En= 0.2-7 MeV  ~ 11% at 1 MeV Experimental setup at ISOLDE 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%

9. b- b- 52K --------> 52Ca 53K --------> 53Ca 2-Neutron-rich nuclei A~50, Z~20 Preliminary results In red: new  transitions In green: new neutron emitter states and transitions 52K decay  detection of both low and high energy neutrons 53K decay  only part of the statistics Comparison with theory for 51,52,53Ca in progress (E. Caurier, F. Nowacki, IReS)

10. Conclusions & Perspectives We have 2 experimental setup which are performing to explore the nuclear structure: TAgS LEND-TONNERRE coupling Efficient neutron detection Effective interaction, shell order Neutron-rich nuclei near the closed shell 35,36Al, Cu, Zn… High  efficiency study of N~Z nuclei  deformation A~80  CVC test 74Rb …  mirror decays 71Kr, 75Sr Such investigations can be performed using any low energy beams at ISOLDE, Ganil, Alto…

11. 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)

12. Collaboration • 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

14. Neutrons transmission

15. Efficiency of neutrons detector : Tonnerre, LEND