Wolfram KORTEN 1 Euroschool Leuven – Septemberi 2009 Coulomb excitation with radioactive ion beams Motivation and introductionMotivation and introduction Theoretical aspects of Coulomb excitation Experimental considerations, set-ups and analysis techniquesExperimental considerations, set-ups and analysis techniques Recent highlights and future perspectivesRecent highlights and future perspectives Lecture given at the Euroschool 2009 in Leuven Wolfram KORTEN CEA Saclay

Wolfram KORTEN 2 Euroschool Leuven – Septemberi 2009 Experiments with Miniball at ISOLDE-Cern

Wolfram KORTEN 3 Euroschool Leuven – Septemberi 2009 Coulomb excitation set up at Rex-Isolde Germanium detector array: Miniball 8 triple cluster Ge detectors, each consisting of three 6-fold segmented HPGe detectors Particle detector Double-Sided Si Strip Detector 1 st post-accelerated beam and Coulomb excitation in 2001

Wolfram KORTEN 4 Euroschool Leuven – Septemberi 2009 O. Niedermaier et al., PRL94, (2005) M. Scheidlitz, P. Reiter et al. in preparation Excitation probability normalised to target excitation (Ni, Ag) Extraction of electromagnetic matrix elements Coulomb excitation of 30,32 Mg at Rex-Isolde/CERN  limits of the “island of inversion” (measurement of    Corrections needed for beam contamination, possible 2 nd order exc.

Wolfram KORTEN 5 Euroschool Leuven – Septemberi 2009 Limits of the 1 st order perturbation analysis 1 st order perturbation theory requires:  Only excitation of the first 2 + state is relevant  “Virtual” excitations of higher lying states are negligible W. Schwerdtfeger et al., PRL 103, (2009) EE

Wolfram KORTEN 6 Euroschool Leuven – Septemberi 2009 Comparison with high-energy Coulomb excitation O. Niedermaier et al., PRL94, (2005) Good agreement between low-energy (“safe”) Coulomb excitation and some of the results obtained from electromagnetic excitation at high energies

Wolfram KORTEN 7 Euroschool Leuven – Septemberi 2009 Coulomb Excitation of Na, 21 Ne Bambino Θ = o Pb shielding 1x10cm collimator plastic scintillator 1 st TIGRESS Experiment, Aug 2006

Wolfram KORTEN 8 Euroschool Leuven – Septemberi 2009 Properties of mirror nuclei 21 Na/ 21 Ne with δ(E2/M1; 5/2 + →3/2 + ) = +0.05(2)  B(E2) = 14  12 W.u. with δ(E2/M1; 5/2 + →3/2 + ) = (1)  B(E2;3/2 +  5/2 + ) = 24  3 W.u.  (5/2 + ) = 1/ tot = [ (M1;5/2 +  3/2 + ) + (E2; 5/2 +  3/2 + )] -1 with I(M1) >> I(E2)

Wolfram KORTEN 9 Euroschool Leuven – Septemberi Ne, 21 Na Heavy-ion gated γ-ray spectra Clean γ-ray spectra with negligible influence of 511 keV due to intense beam β + activity For Ti Doppler correction shows both 46 Ti and 48 Ti 2 + decay transitions

Wolfram KORTEN 10 Euroschool Leuven – Septemberi 2009 GOSIA analysis and results 21 Ne Present workPrior work [1] B(E2; 5/2 + →3/2 + )80 ± 6 e 2 fm 4 83 ± 10 e 2 fm 4 δ(E2/M1) (5/2 + →3/2 + ) ± ± Na Present workPrior work [1] B(E2; 5/2 + →3/2 + )124 ± 9 e 2 fm 4 48 ± 41 e 2 fm 4 δ(E2/M1) (5/2 + →3/2 + ) ± ± 0.02 [1] R.B. Firestone, NDS 103 (2004) 269 with NNDC 10/10/2006 erratum “Wrong” M1/E2 mixing  Stronger E2 component than previously reported Comprehensive Error analysis includes uncertainties in beam energy, target thickness, detector geometry (Clovers), unknown matrix elements and their signs, etc. M.A. Schumacher et al., PRC78 (2008) γ ray yields of 5/2 +  3/2 + transition were measured in coincidence with θ and φ gates on the recoiling ions. Matrix elements were fit to the measured yields using the GOSIA search code assuming the following level scheme. Known lifetimes and branching ratios as input parameters

Wolfram KORTEN 11 Euroschool Leuven – Septemberi st TIGRESS experiment at ISAC-II: Aug 2007 Electronics shack Lead shielding wall Six tigress modules mounted on one half of the mechanical support structure BAMBINO CD-S3 θ = deg. Beam dump on rails Faraday cup YAP:Ce Scintillator Channeltron detector

Wolfram KORTEN 12 Euroschool Leuven – Septemberi 2009 Coulomb Excitation Coulex of 29 Na: Probing the Transition to the Island of Inversion 29 Na beam ~ 400 ions/s, 110 Pd target 2.94 mg/cm 2 TIGRESS-Bambino Coincidences: ~ Hz Room background in TIGRESS: ~ 1.2 kHz 72 keV 29 Na 374 keV 110 Pd A Hurst et al Phys Lett B674(2009) 168 B(E2) = 0.237(21) eb Consistent with MCSM prediction of Otsuka large B(E2) requires narrowing sd-pf (N=20) shell gap

Wolfram KORTEN 13 Euroschool Leuven – Septemberi 2009 Shape coexistence in N=28 isotones R. Rodríguez-Guzmán, PRC 65, Ca Ca Ca Ca Ca Ar Ca s Ar Ar y Ar m Ar s Ar s S S m S s S s S ms S ms Si s Si s Si 38 >1  s Si ms Si ms Si ms Mg ms Mg ms Mg ms Mg 38 >260 ns Mg 40 1 ms M. Girod Bruyères-le-Châtel Rapid onset of deformation in N~28 nuclei below Ca ? All N=28 isotones predicted to show shape coexistence Precision measurement of e.m. matrix elements in 44 Ar

Wolfram KORTEN 14 Euroschool Leuven – Septemberi 2009 Coulomb excitation set-up for RIBs (ex. SPIRAL) Double-sided Si detector 48 rings  16 sectors 16 large Ge Clover detectors 4  4 segmented photopeak efficiency  = 20%

Wolfram KORTEN 15 Euroschool Leuven – Septemberi 2009 B. Fornal et al., EPJA 7, 147 (2000) (4 + ) (6 + ) deep inelastic (2 + ) J. Mrazek et al., Nucl. Phys. A 734, E65 (2004) beta decay SPIRAL beam 44 Ar 3·10 5 pps 2.8·A MeV (Ag) 3.8·A MeV (Pb) EXOGAM 109 Ag DSSD 208 Pb 44 Ar Ag  cm =[35°, 72°] 2+0+2+ Ar 109 Ag 44 Ar Pb  cm =[67°, 130°] (2 + )  (0 + )  0+2+ (2 + )  Coulomb excitation of 44 Ar at SPIRAL / GANIL

Wolfram KORTEN 16 Euroschool Leuven – Septemberi 2009 Determination of quadrupole moments b projectile target The excitation cross section is a direct measure of the E matrix elements. IfIf 1 st order: IiIi 2 nd order: IiIi IfIf ImIm reorientation effect: IfIf IiIi MfMf Sensitivity to Q 2 by varying Z,   (a,v  )

Wolfram KORTEN 17 Euroschool Leuven – Septemberi 2009 Determination of quadrupole moments  differential measurement of Coulomb excitation cross section  extract both transitional and diagonal matrix elements  B(E2) and spectroscopic quadrupole moment Q s  integral measurement is not sensitive to Q s   lifetime measurement  extract B(E2) independent of Q s b projectile target The excitation cross section is a direct measure of the E matrix elements. IfIf 1 st order: IiIi 2 nd order: IiIi IfIf ImIm reorientation effect: IfIf IiIi MfMf

Wolfram KORTEN 18 Euroschool Leuven – Septemberi 2009 Coulomb excitation of 44 Ar at SPIRAL / GANIL (10) 4.6(8) 0+0+ experiment B(E2;  ) in e 2 fm 4 (4 + ) Q s =  8(3) e fm theory HFB+GCM(GOA) Q s =+7 e fm 2 Q s =  7.3 e fm 2 Q s =  14 e fm  good agreement for B(E2) and Q  energy spectrum too spread out Ag target, 35°  cm  70° Ag target, 70°  cm  130°Pb target, 30°  cm  130°

Wolfram KORTEN 19 Euroschool Leuven – Septemberi 2009 Shape coexistence around A=70 74 Kr expected e.g. in: 74 Kr Se Se Kr oblateprolate Possible 0 + shape isomers and configuration mixing

20  70 Se on 104 Pd at 2.94 MeV/u  integral measurement  excitation probability P(2 + ) via normalization to known 104 Pd A.M. Hurst et al., PRL 98, (2007) (Univ. Liverpool) P 2+ depends on  transitional matrix element B(E2)  diagonal matrix element Q 0  one measurement, but two unknowns !  (2 + ) = 1.5(3) ps J. Heese et al., Z. Phys. A 325, 45 (1986) Coulomb excitation probability (1  ) 68 Se intermediate-energy Coulex GANIL E. Clément et al., NIM A 587, 292 (2008) ? Coulomb excitation of 70 Se at CERN / ISOLDE

Wolfram KORTEN 21 Euroschool Leuven – Septemberi 2009 Recoil-Distance Doppler Shift Method gamma rays emitted target and stopper foil at distance d  in flight  Doppler-shifted peak lifetime extracted from intensities as a function of distance d  at rest  narrow peak at E 0

22 Lifetimes in 70 Se revisited GASP and Köln Plunger at Legnaro 40 Ca( 36 Ar,  2p) 70 Se stopped shifted beam Recoil-distance Doppler shift 70 Se 2 +  0 +  literature value:  = 1.5(3) ps J. Heese et al., Z. Phys. A 325, 45 (1986)  new lifetime for 2 + in 70 Se:  = 3.2(2) ps J. Ljungvall et al., Phys. Rev. Lett. 100, (2008) Heese et al. Ljungvall et al.

Wolfram KORTEN 23 Euroschool Leuven – Septemberi 2009 Coulomb excitation of 74,76 Kr at SPIRAL SPIRAL beams 76 Kr 5  10 5 pps 74 Kr 10 4 pps 4.5 MeV/u EXOGAM Pb Acta Phys. Pol. B 36, 1281 (2005)

Wolfram KORTEN 24 Euroschool Leuven – Septemberi 2009 Shape coexistence in 74 Kr [24°, 55°][55°, 74°][67°, 97°][97°, 145°] 74 Kr    E. Clément et al., Phys. Rev. C 75, (2007)  74 Kr Pb at 4.7 MeV/u (SPIRAL)  multi-step Coulomb excitation   -ray yields as function of scattering angle (differential excitation cross section)  experimental spectroscopic data (lifetimes, branching ratios)  least squares fit of ~ 30 matrix elements (transitional and diagonal)

Wolfram KORTEN 25 Euroschool Leuven – Septemberi 2009 Life time results in 74,76 Kr Fusion-evaporation reactions :  40 Ca( 40 Ca,a2p) 74 Kr  40 Ca( 40 Ca,4p) 76 Kr 74 Kr Differential decay curve method: J. Roth et al., J.Phys.G, L25 (1984) 23.5(1.9) ps13.2 (7) ps B. Wörmann et al., NPA 431, 170 (1984) 35.3 (1.0) ps4.8 (5) ps Kr34.5 (6) ps4.9 (3) ps 76 Kr41.4 (6) ps3.7 (2) ps

Wolfram KORTEN 26 Euroschool Leuven – Septemberi 2009 Sensitivity to quadrupole moments 74 Kr  prolate shape full  2 minimization: negative matrix element (positive quadrupole moment Q 0 )  oblate shape positive matrix element (negative quadrupole moment Q 0 ) 74 Kr

Wolfram KORTEN 27 Euroschool Leuven – Septemberi 2009 Quadrupole moments (Q 0 ) in 74 Kr and 76 Kr 74 Kr 76 Kr (4 + )  direct confirmation of the prolate – oblate shape coexistence  first reorientation measurement with radioactive beam eb eb eb  0.86 eb eb eb eb  3.40 eb

Wolfram KORTEN 28 Euroschool Leuven – Septemberi 2009 Full results of Gosia analysis  14 transitional E2 matrix elements  18 transitional E2 matrix elements  4 diagonal E2 matrix elements  5 diagonal E2 matrix elements

Wolfram KORTEN 29 Euroschool Leuven – Septemberi 2009 prolate oblate Q s <0 prolate Q s >0 oblate experimental B(E2;  ) [e 2 fm 4 ] Experimental results and comparison with theory  vibration Calculation HFB-Gogny 5-dim GCM  complete set of e.m. matrix elements, incl. static moments  quantitative understanding of shape coexistence and configuration mixing  triaxiality is the key to reproduce experimental data and shape evolution E. Clément et al., Phys. Rev. C 75, (2007)

Wolfram KORTEN 30 Euroschool Leuven – Septemberi 2009 Coulomb excitation of Zn at Rex-Isolde J. Van de Walle et al., PRL 99, (2007) and PRC 79, (2009) 80 Zn on 108 Pd (2.87 MeV/u, 2.0 mg/cm 2, 3000 pps) Beam contaminants  increase for more exotic beams  must be taken into account when calculating the target excitation Pd Zn

Wolfram KORTEN 31 Euroschool Leuven – Septemberi 2009 Coulomb excitation of Zn at Rex-Isolde two unknowns:  B(E2)  Q s Integral measurement  one observable: total excitation probability 20 ps 28.5 ps 25 ps 74 Zn IfIf IiIi MfMf Life time measurements would reduce B(E2) errors and determine Q 0 possible by using RDDS technique after multi-nucleon transfer reactions

32 Lifetime measurement using multi-nucleon transfer PRISMA / Legnaro Pilot experiment 48 Ca Pb, 6.5 MeV/u J.J. Valiente-Dobón et al. (Legnaro) targets with degraders at fixed distances compact plunger for multi-nucleon transfer reactions to be used at PRISMA (LNL) and VAMOS (GANIL) First GANIL experiment (VAMOS + EXOGAM) 238 U + 64 Ni, 6.5 MeV/u (inverse kinematics) lifetime measurement in neutron-rich nuclei below 68 Ni ( )

Wolfram KORTEN 33 Euroschool Leuven – Septemberi 2009  Opportunity to study a new doubly magic nucleus  Study collectivity of N=82, Z=50 core excitation  High E(2 + ) ~ 4MeV + small B(E2) + weak beam (10 4 pps)  very low event rate -Employ high efficiency BaF 2  -array ~ 40% full-energy at 4 MeV -Use high-Z target ( 48 Ti) -Run at higher (“unsafe”) energies (495 MeV and 470 MeV) -Limit distance of closest approach by looking only at forward angles in center of mass Coulomb Excitation of 132 Sn at HRIBF

Wolfram KORTEN 34 Euroschool Leuven – Septemberi 2009 BaF 2 array (150 crystals) for gamma-rays Beam courtesy of D. Radford Setup for 132,134 Sn Coulomb Excitation

Wolfram KORTEN 35 Euroschool Leuven – Septemberi 2009 Beam “CD”-type Si detector for scattered Sn and Ti 7 cm diameter 48 radial strips 16 sectors  LAB ~ 7° – 25°  CM ~ 30° - 160° Setup for 132,134 Sn Coulomb Excitation courtesy of D. Radford

Wolfram KORTEN 36 Euroschool Leuven – Septemberi Sn beam, doubly stripped - 96% pure x 10 5 ions/s & 3.56 MeV/u 48 Ti target High  efficiency (~ 40%) Two-week experiment Fast  –ion coincidences to suppress background First results on 132 Sn

Wolfram KORTEN 37 Euroschool Leuven – Septemberi Sn beam, doubly stripped - 96% pure x 10 5 ions/s & 3.56 MeV/u 48 Ti target High  efficiency (~ 40%) Two-week experiment Fast  –ion coincidences to suppress background Sample gamma-ray spectrum:  ~30% of data  Crystal gain matching & background suppression not yet optimum 48 Ti 2 +  keV; 1.2 barns 132 Sn 2 +  keV 470 MeV  cm < 110° First results on 132 Sn

Wolfram KORTEN 38 Euroschool Leuven – Septemberi Sn beam, doubly stripped - 96% pure x 10 5 ions/s & 3.56 MeV/u 48 Ti target High  efficiency (~ 40%) Two-week experiment Fast  –ion coincidences to suppress background B(E2; 0 +  2 + ) ~ 0.11(3) e 2 b 2 First results on 132 Sn Sample gamma-ray spectrum:  ~30% of data  Crystal gain matching & background suppression not yet optimum 48 Ti 2 +  keV; 1.2 barns 132 Sn 2 +  keV 470 MeV  cm < 110° R. Varner et al., EPJ. A 25, s01, 391 (2005)

Wolfram KORTEN 39 Euroschool Leuven – Septemberi 2009  132 Sn: B(E2) ~ 0.11(3) e 2 b 2 14% Isoscalar E2 EWSR  134 Sn: B(E2) = 0.029(5) e 2 b 2 Coulomb Excitation Results for Sn isotopes B(E2; 0 +  2 + ) (e 2 b 2 ) A (Sn Isotopes) E(2 + ) (keV) New facilities needed in order to fully explore this mass region

Wolfram KORTEN 40 Euroschool Leuven – Septemberi Na, 30,31,32 Mg Z=28 Z=50N=40 Z=82 20 N=50 N=82 Drip lines and shell Structure in light nuclei Drip-line nuclei: 10 Be Mirror nuclei : 20,21 Na, 21 Ne The “island of inversion” : 29 Na, 30,31,32 Mg Coulomb excitation studies with low-energy RIBs 10 Be 20,21 Na, 21 Ne

Wolfram KORTEN 41 Euroschool Leuven – Septemberi ,69,71,73 Cu, 68 Cu, 70(m) Cu 68 Ni 74,76,78,80 Zn, 82 Ge 106,108,110 Sn 122,124 Cd, Sn Te, 138,140 Xe 140,148,150 Ba Z=28 Z=50N=40 Z=82 20 N=50 N=82 Evolution of Shell Structure far from stability 44 Ar (N=28) Ni (Z=28, N=40-50) : 68 Ni, 67,69,71,73 Ci, 68,70(m) Cu, 74,76,78,80 Zn, 61 Mn, 61 Fe 100 Sn : 106,108,110 Sn, 100,102,104 Cd 132 Sn : (Z=50, N=82) Cd, Sn, Te, 140 Ba Coulomb excitation studies with low-energy RIBs

Wolfram KORTEN 42 Euroschool Leuven – Septemberi 2009 Evolution of nuclear shapes and shape coexistence N=Z  34: 70 Se, 74,76 Kr, N  60: Kr, 96 Sr N  104: 182,184,186,188 Hg, 202,204 Rn 74,76 Kr 70 Se Z=28 Z=50N=40 Z=82 20 N=50 N=82 96 Sr, Kr 182,184,186,188 Hg 202,204 Rn Coulomb excitation studies with low-energy RIBs

Wolfram KORTEN 43 Euroschool Leuven – Septemberi 2009 Perspectives Ni 28 Cu 29 Zn 30 Ga 31 Ge 32 As 33 Se 34 Br 35 Kr 36 Rb 37 Sr 38 Y 39 Zr 40 Nb 41 Mo42 Tc 43 Ru 44 Rh Pd 46 Ag 47 Cd 48 In 49 Sn 50 Sb 51 Te 52 I 53 Xe 54 Cs 55 Ba 56 La 57 Ce 58 Pr 59 Nd 60 Pm 61 Sm 62 Eu 63 Gd 64 Tb 65 Dy 66 Ho Quadrupole deformation zone Spherical robust gaps Octupole deformation gaps Spherical fragile gaps Deformed gaps courtesy D. Verney (IPNO)

Wolfram KORTEN 44 Euroschool Leuven – Septemberi 2009 M. Girod CEA Bruyères-le-Châtel Shapes in neutron-rich A=100 nuclei 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 Kr 98 Sr 100 Zr J. Skalski et al., NPA 617, 282 (1997)

Wolfram KORTEN 45 Euroschool Leuven – Septemberi 2009 Coulomb excitation measurement towards 100 Sn Sn+ 2.8 MeV/u A. Ekstrom et al., PRL101 (012502) 2008