Lifetime measurement in 74 Ni: probing the core polarisation around the double magic 78 Ni G. de Angelis, D.R. Napoli, E. Sahin, J.J. Valiente-Dobon INFN, Laboratori Nazionali di Legnaro, Legnaro, Italy S. Aydin, D. Bazzacco, E. Farnea, S. Lenzi, S. Lunardi, R. Menegazzo, D. Mengoni, F. Recchia, C. Ur Dipartimento di Fisica and INFN, Sezione di Padova, Padova, Italy P. Boutachkov, C. Domingo-Pardo, J. Gerl, M. Gorska, E. Merchan, S. Pietri, H.J. Wollersheim GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, Germany M. Bostan, N. Erduran, A. Kusoglu University of Istanbul, Istanbul, Turkey M. Doncel, B. Quintana University of Salamanca, Spain A. Algora, A. Gadea, T. Huyuk, B. Rubio IFIC Instituto de Fisica Corpuscular, Valencia, Spain

2 Scientific motivation Inversion of the single particle orbitals Particle-hole excitations across the shell gap (Z=28) neutrons in g 9/2 68 Ni 78 Ni Z=28 T. Otsuka et al. PRL 95, (2005)‏ f 5/2 f 7/2 proton neutron g 9/2 N=50 Study the tensor part of the (spin-isospin term of the) residual interaction. Attraction between orbitals with antiparallel spin configuration. Smaller Z=28 gap for protons in the pf-shell, and inversion of single-particle orbitals. Z=28 j>j> j>j> j<j<

3 Scientific motivation f 5/2 f 7/2 proton neutron g 9/2 N=50 j>j> j>j> j<j< 68 Ni 70 Ni 72 Ni 74 Ni 76 Ni 78 Ni Study the tensor part of the (spin-isospin term of the) residual interaction. Attraction between orbitals with antiparallel spin configuration. Smaller Z=28 gap for protons in the pf-shell, and inversion of single-particle orbitals. J.van de Walle et al., Phys. Rev. Lett. 99, (2008). Z=28 Zn g 9/2

4 B(E2:2 +  0 + ) ~200 e 2 fm 4 72 Ni  ~2 ps 70,72 Ni Isotopes at LN Legnaro Core polarization due to the tensor mechanism around 78 Ni 70 Ni 72 Ni LNL, Multi-nucleon Transfer Reactions O. Perru et al. PRL 96, (2006) O. Sorlin et al. PRL 88, (2002) A. Ansari, P. Ring, PRC 74, (2006) Eda Sahin*, Maria Doncel**, Andreas G ö rgen*** et al. * INFN-LNL, Legnaro (PD), Italy ** LRI, University Salamanca, Spain ***CEA, Saclay,IRFU/SPhN, France Lifetime measurement in neutron-rich Ni, Cu, and Zn isotopes neutron polarization charge of 1.5 e is needed in the SM calculation in order to reproduce the experimental results!

5 74 Ni at Core polarization due to the tensor mechanism around 78 Ni 70 Ni 74 Ni O. Perru et al. PRL 96, (2006) O. Sorlin et al. PRL 88, (2002) A. Ansari, P. Ring, PRC 74, (2006) 86 Kr 1x10 10 pps 75 Cu 100 pps 74 Ni* + p 75 Cu

Line shape effect of first 2 + in 74 Ni vs. lifetime Realistic MC Simulation of a fragmentation experiment: DSAM Analysis MeV/u Fe Target (500mg/cm 2 ) 74 Ni keV 74 Ni  = 0.5 to 1.5 ps  = ? Zoom

Summary & Outlook The aim of the experiment at GSI would be to make one step further, compared to the present experimental programme at LNL (on the Ni, Cu and Zn isotopes), and measure the lifetime of 74 Ni via the DSAM technique. Such measurement will represent the closest measurement to 78 Ni in the seniority parabola scheme of B(E2) vs. Neutron Number, and will allow for a more detailed undertanding of the core polarisation mechanism and the tensor component of the spin-isospin term in the residual interaction. We think that this is a GSI-AGATA unique experiment, because of the high secondary beam intensities required to populate the 2 + in 74 Ni, and because of the high angular sensitivity needed for the DSAM analysis.

8 82 Se MeV CLARA-PRISMA Θ PRISMA =Θ Grazing =64˚ Deep-inelastic and multi-nucleon transfer reactions 71 Cu 73 Cu 75 Cu Cu Isotopes Evolution of the Z=28 shell closure g 9/2  p 3/2  f 5/2  p 1/2  p 3/2  2 + ( A-1 Ni)‏ 3/2 - 5/2 - 1/2 - 7/ Cu 38 7/2 - (  f 7/2 ) Cu Cu Cu Cu 46 f 5/2 -p 3/2 inversion 1f 7/2 2p 3/2 1f 5/2 2p 1/2 1g 9/2  N=40 Z=28 K.T. Flanagan et. al, PRL 103, (2009) Nuclear spin and magnetic moment ISOLDE proved the inversion

9 Coulomb excitation with radioactive beams at REX-ISOLDE Cu Isotopes Evolution of the Z=28 shell closure NiCu 71 Cu 73 Cu  ~2 ps B(E2) values are essential in order to characterize the levels. Single-particle excitations across the Z=28 shell gap will provide the information on the Z=28 shell gap size and therefore, its evolution.  p 3/2  2 + N-50 Z=28  f 5/2  2 +  p 3/2  2 + (  f 7/2 ) -1  ~2ps  ~25ps  ~10ps

10 excitation probability depends on  transitional matrix element  2 +  M(E2)  0 +   B(E2;0 + →2 + )  diagonal matrix element  2 +  M(E2)  2 +   Q s (2 + ) 20 ps 28.5 ps 25 ps 74 Zn MfMf J. Van de Walle et al., PRL 99, (2007) PRC 79, (2009) Coulomb excitation of radioactive Zn at ISOLDE  integral measurement of excitation probability  relative to target excitation B(E2) values extracted under the assumption that Q s (2 + ) = 0 combine Coulomb excitation and lifetimes  find correct B(E2) value  AND quadrupole moment combine Coulomb excitation and lifetimes  find correct B(E2) value  AND quadrupole moment Zn isotopes Shape and collectivity

11 Proposed Experiment Multi-nucleon transfer reactions 76 Ge E( 76 Ge)=500 MeV SETUP: AD coupled to PRISMA (at 59  ) + Köln Plunger AIM: To measure the lifetime of the excited states in 70,72 Ni, 71,73 Cu, and Zn isotopes using RDDS technique beam targetdegrader

12 AGATA Demonstrator vs. CLARA A novel technique that combines the RDDS method with CLARA-PRISMA has been successfully performed using deep-inelastic reactions AGATA CLARA M.C. Simulations (by D. Mengoni) 48 Ca 310MeV Pb for lifetime measurement gain ~ 5 Comparison between the Diff.plunger lifetime experiment performed with CLARA and with the AGATA D.

Distances Energy of the Projectile-like ions = 320 MeV  =28.5  m/ps   =9.5% Lifetimes (ps)Distances (  m) 230, 60, 120, 250* 25500, 1000, 2000

14 Rate Evaluation 70 Zn MeV CLARA-PRISMA Θ PRISMA =Θ Grazing =64˚ ~100 counts 70 Zn+ 238 U 76 Ge+ 238 U (-4p) (-3p,-2n) (-3p) (-2p,+2n) 66 Fe 65 Co 67 Co 70 Ni 72 Ni 71 Cu 73 Cu 76 Zn 70 Zn+ 238 U 76 Ge+ 238 U GAIN Beam Time 7 days 14 days 2 Beam Intensity 2 pnA 1 Target Thickness 1 mg/cm 2 2 mg/cm 2 2  at 1 MeV (%) (CLARA) 2.6 (AD) 6 ~2 Total Gain Factor : Short Long Distance (  m) Thanks to S. Lenzi

15 Beam Time Request Beam: 76 Ge at 500 MeV provided from the Tandem-ALPI complex Target: 2 mg/cm U Degrader: 4 mg/cm 2 natural Mg Beam Intensity: 2 pnA Cross sections from the GRAZING code (N. Pollarolo et. al)  ( 72 Ni) ~ 100 µb   ( 66 Fe) ~ 100 µb  ( 73 Cu) ~ 750 µb  ( 71 Cu) ~ 250 µb  ( 76 Zn) ~ 2000 µb 14 days of beam time (2 days per distance)

Thank you …

17 RDDS experiment in inverse kinematics: VAMOS  EXOGAM – Plunger beam: 238 U, 6.5 MeV/u target: 64 Ni, 1.5 mg/cm 2 degrader:Mg, 4.7 mg/cm 2 6 distances: 40 – 750 μm ~18 hours per distance 62 Fe 64 Fe J. Ljungvall et al., to be published

18 AGATA Demonstrator vs. EXOGAM Exogam AD at 14cm AGATA Demo. 1  180  11 cm GEANT 4 simulation and AGATA tracking (J. Ljungvall) 3  135  14.5 cm EXOGAM data gain: factor 3 in  singles  more exotic reaction channels factor 10 in  -  coinc.  higher precision in strong channels