W. Korten Nuclear collectivity and shape evolution in exotic nuclei Wolfram KORTEN CEA Saclay DSM/IRFU/SPhN

W. Korten Shapes and shells in exotic nuclei Prolate Oblate Quadrupole deformation of the nuclear ground states M. Girod, CEA Bruyères-le-Châtel  Dominance of prolate ground state shapes over most of the nuclear chart  Islands of oblate nuclei and shape coexistence (N~Z, A~100, …)  Erosion of shell gaps leads to (strongly) deformed nuclei at N=20, 28 and 40

W. Korten Evolution of collectivity around N=40 Persistence of N=40 sub-shell closure beyond 68 Ni ?   correlations stronger than N=40 gap for Z  28  increased collectivity with filling of g 9/2 Previous experimental results:  Coulomb excitation of Ge at ORNL / HRIBF E. Padilla-Rodal et al., PRL 94, (2005)  Coulomb excitation of Zn at CERN / ISOLDE J. Van de Walle et al., PRL 99, (2007) J. Van de Walle et al., PRC 79, (2009) New experimental approach  Lifetime measurements after MNT/DIC B(E2) in Fe  EXOGAM/VAMOS at GANIL B(E2) in Zn  AGATA/PRISME at LNL N=50 Z=28 N=40

W. Korten Experimental methods: Coulomb excitation Coulomb excitation of Zn at CERN / ISOLDE  A Zn on 108 Pd/ 120 Sn at ≈2.8 MeV/u  integral measurement  excitation probability via normalization to target  one observable:  (2 + ), two unknowns: B(E2), Q s 20 ps 28.5 ps 25 ps 74 Zn two unknowns:  B(E2; 0 +  2 + )  Q s (2 + ) IfIf IiIi MfMf = 0 ! J. Van de Walle et al., PRL 99, (2007) J. Van de Walle et al., PRC 79, (2009)

W. Korten Coulomb excitation vs. lifetime measurement: 70 Se Coulomb excitation of 70 Se at CERN / ISOLDE  70 Se on 104 Pd at 2.94 MeV/u  integral measurement  excitation probability via normalization to target  one observable:  (2 + ), two unknowns: B(E2), Q s A.M. Hurst et al., PRL 98, (2007) Heese et al.  = 1.5(3) ps Z. Phys. A 325, 45 (1986) J. Ljungvall et al., PRL 100, (2008) RDDS measurement at LNL  GASP and Köln Plunger  40 Ca( 36 Ar,  2p) 70 Se  12 distances 8  400  m  gated from above  side feeding effects eliminated  70 Se,  (2 + )=3.2(2) ps Counts/3keV E  [keV]

W. Korten Collectivity in neutron-rich nuclei around N=40 -2p : 62 Fe 74 Zn -2p+2n: 64 Fe 76 Zn 238 U MeV/u VAMOS + EXOGAM 76 Ge MeV/u PRISMA + AGATA Demo. Recoil-Distance Doppler-shift (RDDS) lifetime measurements in nuclei produced by multi-nucleon transfer or deep-inelastic reactions N=40 N=50 Z=28

W. Korten RDDS experiment in inverse kinematics at VAMOS Q Q D 45° drift chamber: x,y Se - D: trigger, t 1 ionisation chamber:  E silicon wall: E, t 2 64 Fe 64 Ni Mg v1v1 v2v2 1x180° 3x135° 5x90° 238 U, 6.5 MeV/u

W. Korten The Recoil-Distance Doppler-Shift technique  aft ~ 8.5%  bef ~10% EE E’  EE J. Valiente-Dobón et al., PRL 102 (2009) Differential RDDS technique combined with deep-inelastic (or multi-nucleon transfer) reactions was pioneered at LNL using the CLARA-PRISMA set-up

W. Korten 64 Fe Lifetimes in neutron-rich Fe isotopes 238 U MeV/u J. Ljungval et al., PRC C 81, (R) (2010) 62 Fe 64 Fe

W. Korten Collectivity in neutron-rich Fe isotopes J. Ljungval et al., PRC C 81, (R) (2010) W. Rother et al., PRL 106, (2011)

W. Korten  f 7/2 p 3/2 f 5/2 p 1/2 g 9/2 d 5/2 66 Fe  Importance of neutron g 9/2 (and d 5/2 ) intruder orbitals Collectivity in neutron-rich Fe isotopes J. Ljungval et al., PRC C 81, (R) (2010) W. Rother et al., PRL 106, (2011)

W. Korten Collectivity in neutron-rich nuclei around N=40 -1p : 63 Co -1p+2n: 65 Co 238 U MeV/u VAMOS + EXOGAM N=40 N=50 Lifetime measurements in neutron-rich Fe and Co isotopes Z=28

W. Korten Fe and Ni Core coupled states ? Structure of the ground state ? Structure of odd-mass Co isotopes

W. Korten Lifetime measurement in 63,65 Co “Fe-like” 3/2 -  7/2 - transition A. Dijon et al., PRC 83, (2011)  Direct lifetime extraction possible T 1/2 =15.4 ± 1.8 ps B(E2)= 3.71 ± 0.43 W.u

W. Korten Lifetime measurement in 63,65 Co  lifetime extraction requires selection in excitation energy T 1/2 =0.9 ± 0.4 ps B(E2)= 12.2 ±5.4 W.u “Ni-like” 9/2 -  7/2 - transition A. Dijon et al., PRC 83, (2011)  Direct lifetime extraction possible T 1/2 =15.4 ± 1.8 ps B(E2)= 3.71 ± 0.43 W.u “Fe-like” 3/2 -  7/2 - transition

W. Korten Collectivity in neutron-rich nuclei around N=40 -2p : 74 Zn -2p+2n: 76 Zn 76 Ge MeV/u PRISMA + AGATA Demo. Lifetime measurements in neutron-rich Zn and Co isotopes N=40 N=50 Z=28

W. Korten Lifetime measurement in neutron-rich Ni, Cu and Zn isotopes Spokespersons: A. Goergen (Saclay), M. Doncel (U. Salamanca), E. Sahin (LNL) AGATA experiment performed in June 2010 at the LNL using multi-nucleon transfer reaction ( 76 Ge U)

W. Korten The PRISMA spectrometer at LNL Quadrupole Dipole MCP MWPPAC IC Angular range: -30º to 140º X-Y, time E,  E AGATA 6.5 m (TOF)

W. Korten Charge state determination and selection Z identification Mass separation (all distances together) Particle identification with PRISMA

W. Korten Multi-nucleon transfer reactions in direct kinematics: 76 Ge+ 238 U Recoil-Distance Doppler Shift (RDDS) experiments  differential plunger Lifetime experiments with AGATA at PRISMA 76 Ge beam (577 MeV, 0.3pnA) 238 U target (1.4 mg/cm 2 ) Ta backing (1.2mg/cm 2 ) Nb degrader (4 mg/cm 2 )  khZ Ge singles rate

W. Korten RDDS with EXOGAM vs. AGATA Demonstrator Exogam v AD at 14cm AGATA Demo. 6 times more counts for same peak separation for all angles 180  detector at 11 cm 135  detectors at 14.5 cm GEANT 4 simulation and AGATA tracking (J. Ljungvall)

W. Korten  Life time measurements in 72,74 Zn with the differential plunger technique and the AGATA demonstrator in Legnaro (June 2010) 72 Zn Collectivity in neutron-rich Zn isotopes 2 + decay curve

W. Korten RDDS spectra of neutron-rich Zn isotopes

W. Korten RDDS spectra of neutron-rich Zn isotopes C. Louchart et al, to be published

W. Korten RDDS analysis: Differential Decay Curve method  and  v = 30  m/ps 100  m 200  m 500  m 1000  m 1900  m C. Louchart et al, to be published

W. Korten RDDS analysis: Differential Decay Curve method

W. Korten Collectivity in neutron-rich Zn isotopes References: [1] J.K. Tuli, Nucl. Data Sheets 103 (2004) 389 [2] B. Prytychenko arXiv: v2 (2011) [3] D. Muecher et al., PRC 79 (2009) [4] S. Leenhardt et al., EPJ A 14 (2002) 1 [5] J. Van de Walle et al., PRC79 (2009) [6] M. Niikura et al., PRC (2012) in press [7] E. Clement, priv. comm. C. Louchart et al, to be published 20 ps 28.5 ps 25 ps Quadrupole moment Q(2 + ) of 74 Zn  Preference for oblate shape of 74 Zn

W. Korten J.-P. Delaroche et al, PRC 81, (2010) M. Honma et al, PRC 80, (2009) 74 Zn HFB D1S From lifetime experiment M. Niikura et al. arXiv : v1 (2011) J. Van de Walle et al, PRL 99, (2007) J.-P. Delaroche et al, PRC 81, (2010) M. Honma et al, PRC 80, (2009) 74 Zn Quadrupole collectivity of 74 Zn  B(E2) in accordance with shell model and HFB D1S calculation  Q(2 + ) >0 indicates “oblate” shape not supported by the shell model nor the HFB D1S calculation

W. Korten  Maximum of collectivity at N~42  B(E2; 2 +  0 + ) values in agreement with previous measurements  lower B(E2; 4 +  2 + ) values with minimum at N=44  Discrepancy for  4 + ) in 74 Zn with previous (Coulomb excitation) measurement 70 Zn: D. Mücher et al. PRC (2009) 74 Zn: J. Van de Walle et al. PRC (2009) Collectivity in neutron-rich Zn isotopes

W. Korten  B(E2; 2 + -> 0 + ) values are in agreement with shell model calculations  Beyond mean field calculation over estimate the collectivity in particular for B(E2; 4 + -> 2 + ) values  Shell model calculations do not reproduce the trend of the systematics for B(E2; 4 + -> 2 + ) values Collectivity in neutron-rich Zn isotopes

W. Korten Collectivity in neutron-rich Zn isotopes

W. Korten Collectivity in neutron-rich Zn isotopes R(E2) <1 for all Zn isotopes (except 70 Zn at N=40) similar to Ca and (partially) Cr isotopes, but different from Ti (Z=22)

W. Korten Collectivity in neutron-rich nuclei around N=40 -3p-2n : 71 Cu -3p: 73 Cu 76 Ge MeV/u PRISMA + AGATA Demo. Lifetime measurement in neutron-rich Zn and Cu isotopes N=40 N=50 Z=28

W. Korten Experimental results: 71 Cu M. Doncel et al, to be published

W. Korten Reduced transition probability RDDS approach considering the unshifted peak only 7/2 - → 3/2 - T 1/2 = 14 (11) ps Experimental results: 71 Cu M. Doncel et al, to be published

W. Korten Shell-model calculations using the fpg valence space do not reproduce the B(E2) values for Cu isotopes. Inclusion of the neutron d 5/2 orbital (1)I. Stefanescu et al., Phys. Rev. Lett 100 (2008) (2)N.A. Smirnova et al., Phys. Rev. C (2004) (3) K. Sieja et al., Private Communication. Experimental results: 71 Cu

W. Korten Calculations performed with the ANTOINE code allowing 8p-8h excitations (K. Sieja) Experimental results: 71 Cu M. Doncel et al, to be published

W. Korten Occupation numbers for neutrons and protons: The inclusion of the neutron d 5/2 orbital, which is the SU(3) partner of the g 9/2 orbital, leads to an enhancement of the quadrupole contribution. B(E2) values are well reproduced taking into account this contribution not considered in previous shell-model calculations. Different behavior of the proton p 3/2 and f 5/2 orbitals Inclusion of the neutron d 5/2 orbital Different character for the 7/2 - excited states Experimental results: 71 Cu

W. Korten Shape evolution in the A~100 region 96 Sr 98 Sr 100 Sr 102 Sr 104 Sr 94 Sr 92 Sr 100 Zr 102 Zr 104 Zr 106 Zr 98 Zr 96 Zr 94 Zr 94 Kr 96 Kr 100 Kr 102 Kr 98 Kr 92 Kr 90 Kr 92 Se 94 Se 96 Se 98 Se 90 Se 96 Mo 98 Mo 100 Mo 102 Mo 104 Mo 106 Mo 108 Mo 100 Ru 102 Ru 104 Ru 106 Ru 108 Ru  rapid shape changes and shape coexistence expected  accessible with HIE-Isolde and SPIRAL-2

W. Korten Coulomb excitation of 96 Sr at REX-ISOLDE  Large B(E2; 2 +  0 + )  17 W.u.   (2 + ) = 4.9(3) ps  Mixing between spherical and deformed states ?  Static quadrupole moment Q s (2 + )  0  Quasi-vibrational character ?  Equal mixing of prolate and oblate components ?  Coulomb excitation in 98 Sr planned, but need for higher beam energy and intensity  Lifetime measurement to constrain the data 462 (11) e²fm4 < 22 e²fm4 Q s = -6 (9) efm² 399 ( ) e²fm4 < 625 e²fm4 B(E2↓)  Coulomb excitation at 2.8 MeV/u on 120 Sn and 109 Ag targets  Normalisation through known target transitions  Differential and integrated cross section  GOSIA analysis  limited statistics for higher lying 0 + and 2 + states < 152 e²fm4 E. Clement et al., to be published

W. Korten In-flight studies of fission fragments at GANIL Q Q D drift chamber: x,y Se - D: trigger, t 1 ionisation chamber:  E silicon wall: E, t Ru 9 Be Mg v1v1 v2v2 1x180° 3x135° 5x90° 238 U, 6.5 MeV/u Fission fragment production/identification with VAMOS Gamma-ray detection with EXOGAM RDDS experiment using plunger (spring 2011) New results for several neutron-rich nuclei 112 Ru, 118 Cd, many odd-mass isotopes 110 Ru A. Shrivastava, F. Rejmund et al Phys. Rev. C (R) (2009) pioneered by F. Farget et al. (see talk Fr morning)

W. Korten Fission fragment distribution 9 Be( 238 U,ff)X at 6.5 MeV/u

W. Korten Fission fragment mass distribution 9 Be( 238 U,ff)X at 6.5 MeV/u Zr; Mo; Ru Pd; Cd

W. Korten Preliminary fission fragment gamma-ray spectra 9 Be( 238 U,ff)X at 6.5 MeV/u Zr; Mo; Ru Pd; Cd 100 Zr 102 Zr  (I≥4 + ) 104 Mo 106 Mo 108 Mo  (I≥4 + ) 110 Ru  (I≥4 + ) 112 Ru  (I≥4 + ) 114 Ru  (I≥2 + )

W. Korten Preliminary fission fragment gamma-ray spectra 122 Cd 120 Cd 118 Pd 116 Pd

W. Korten Summary and perspectives  Application of Recoil-Distance Doppler-Shift Method to deep-inelastic and fusion-fission reactions is a powerful tool to study (moderately) neutron-rich nuclei  Onset of collectivity in the Fe isotopes below 68 Ni starts already around N~38 and requires inclusion of d 3/2 orbital in shell model calculations  Neutron-rich Zn isotopes show tendency towards oblate deformation in contrast to theoretical expectations; B(E2) ratios of 4 + and 2 + decays are systematically < 1  Perspective for strong progress when using RDDS technique with (2014) and complementary Coulomb excitation experiments using SPIRAL2 and HIE-Isolde

W. Korten Thank you

W. Korten 33.6 μm 99 μm Recent 72 Zn measurement at GANIL (4 + ) (6 + ) Znτ [ps]B(E2) [e 2 fm 4 ] ±7.0304± ±1.8232± ±1.6120± (1.8) M. Niikura et al. Accepted PRC (2012) 18.2(1.4) C. Louchart et al. 5.9(7) C. Louchart et al. I. Celikovic et al. GANIL-VINCA

W. Korten Quadrupole moments in neutron-rich Zn nuclei  focus of ISOLDE experiment was on 80 Zn  new Coulex measurement (~ 3 days)  improve precision for 74,76 Zn significantly  obtain data for 72 Zn (planned in summer 2012) Combined with results from ISOLDE Coulex RDDS lifetime measurement will yield quadrupole moments for 2+ states in 74,76 Zn. J. Van de Walle et al., PRC 79, (2009)

W. Korten DSAM lifetime measurement in 72 Zn

W. Korten All nuclei 20<Z<40 Non-magic nuclei 40<Z<80 R.B. Cakirli et al. PRC 70, (2004) vibrator rotor possible explanation as transition from seniority regime to collective motion ? J.J. Ressler et al. PRC 69, (2004)