New Insights into Nuclear Structure at Extremes of Isospin usng the Stopped RISING Array at GSI Paddy Regan for the Stopped Beam Rising Collaboration Dept. of Physics, University of Surrey Guildford, Surrey, GU2 7XH, UK

RISING Rare Isotopic Spectroscopic GSI = 15 x Cluster germaniums for (the most) exotic gamma-ray spectroscopy

Physics aims of the RISING stopped beam campaign 82 Nb, 86 Tc 54 Ni 130 Cd, N= Pt, N= Zr ~ 190 W, Terra Incognita

Stopped RISING Physics Aims Study the evolution of single-particle / shell structure (shell melting ?) as a function of N:Z ratio. – 56 Ni (N=28 ; Z=28) Emma Johannson Mon. 7.50pm – 100 Sn (N=50: Z=50) – 132 Sn (N=82 : Z=50) Juergen Gerl, Tues am – 208 Pb (N=126 : Z=82) Steve Steer, poster Spin input in fragmentation. Stephane Pietri, poster – High(est) spins in projectile fragmentation Juergen Gerl, Tues am Study the structure of nuclei with the most exotic proton-to-neutron ratios: – Proton drip-line N=Z Adam Garnsworthy, poster – (Very) neutron-rich, Jurgen Gerl, Tues am Nuclear ‘symmetries’ and relevance of quantum numbers: – Isospin, T(N:Z ratio) – Nuclear Deformation,  2 (p-n interactions) – Angular Momentum Projection, K (axial symmetry) – Critical Point Symmetries e.g., X(5)

Accelerator facility at GSI The Accelerators: UNILAC (injector) E=11.4 MeV/n SIS 18Tm corr. U 1 GeV/n Beam Currents: 238 U pps some medium mass nuclei pps (A~130) FRS provides secondary radioactive ion beams: fragmentation or fission of primary beams high secondary beam energies: 100 – 700 MeV/u fully stripped ions

Ion-by-ion identification with the FRS TOF EE Cocktail of secondary, exotic fragments with ~ x00 MeV/u thru. FRS. Separate and identify event-by-event. Chemically independent.

Stopped RISING GSI: 15 x 7 element CLUSTERs Photopeak efficiency >10% at 1.3 MeV. XIA-DGF electronics

Best  -spectrometer ever used in isomer spectroscopy ! The RISING  -ray spectrometer 15 EUROBALL Cluster (105 Ge crystals) digital signal processing via 30 XIA DGF modules Absolute efficiency [%]  -energy [keV] DGF TDC MSU GSI  detection efficiency very high  -ray efficiency high granularity (prompt flash problem) S. Pietri et al., in press NIM B + poster

S. Pietri et al., in press NIM B (2007) High granularity of RISING reduces ‘prompt flash’ problems….~ 7 / 105… DGF timing of flash, comparable to former ‘analog’ timing.

(  g 9/2 ) -2 I=8 + +  g 9/2 ) -2 I=8 + + (  g 9/2 ) -2,4 I=14 +  g 9/2 ) -2,4 I=14 + S. Pietri et al., Nucl. Inst. Meth. B. in press. (2007) I  =12 + isomer N. Marginean et al., PRC67 (2003)

Physics aims of the RISING stopped beam campaign 82 Nb, 86 Tc 54 Ni 130 Cd 204 Pt 106 Zr ~ 190 W, Terra Incognita

S. Pietri et al., RISING data 107 Ag beam

T=0, 1 Competition in Deformed N=Z odd-odd Nuclei Use projectile fragmentation to populate exotic N=Z=41,43 nuclei 82 Nb, 86 Tc. Measure gammas from isomeric decays. Construct (partial) decay schemes Look for energy competition between T=1 (I  =0 + ) and T=0 (I  =1 + ?) lowest states.

Structure of Odd-Odd N=Z Nuclei Even-even core plus one valence proton and one valence neutron in equivalent orbits Neutron-Proton PairingT=1 and T=0Residual InteractionsGround state angular momentum can be 0 +, J min or J max

New Data point ? T=1: I  =0 + T=0 : I  =1 + or (2j) + E (T=0 – T=1) (keV)

82 Nb 86 Tc T 1/2 = 133(20) ns T 1/2 = 1.59(20)  s A.B. Garnsworthy, submitted to PRL

T=1(T=0)T=1(T=0) T=1 82 Nb 86 Tc 82 Zr 86 Mo Level structure of 82 Nb and 86 Tc compared to their T Z =+1 isobars A. Garnsworthy et al., submitted to PRL

A.B. Garnsworthy et al., submitted to PRL

128 keV M1 in 82 Nb gives f =18. First Isospin changing K isomer? *Note, E2 conversion for 128 keV would give unphysical IR~200%. *

Mapping isospin symmetry across the fpg shell.

Physics aims of the RISING stopped beam campaign 82 Nb, 86 Tc 54 Ni 130 Cd 204 Pt 106 Zr

Active Stopper RISING Isomer spectroscopy requires isomers! Would like to be able to do beta-delayed spectroscopy on (neutron-rich) fragments. Problem….implanting ~10 GeV energy followed by ~200 keV in same pixel. Solution? ‘Logarithmic’ pre-amps.

5 cm x 5 cm DSSSD (16 strips by 16 strips = 256 pixels) 3 positions across focal plane, room for 2 detectors deep.

R. Kumar et al.,

190 W isomer decay from 208 Pb beam (poster by G. Farrelly).

On-line beta-delayed gated 190 Ta ions….. Transitions fed in daughter 190 W nucleus by beta decay. 207 keV 2 + → 0 + N. Al-Khomashi, PhD thesis First time we see same nucleus via both isomer decay AND beta-decay.

β-delayed γ-rays in 192 W – Decay of 192 Ta

P.D. Stevenson et al., Phys. Rev. C72 (2005) W 188 W 192 W

205 Au 190 Ta 192 Ta 203 Au 188 Ta 194 Re 198 Ir 202 Ir

Summary of Stopped RISING to Date 2006 passive stopper (isomer) experiments –N~Z isomers, isospin symmetry/pairing studies around 56 Ni (Rudolph) and highly deformed A~80 N=Z (PHR). –N~126 seniority isomers ( 204 Pt) (Podolyak) –Neutron-rich ~ 132 Sn nuclei with 136 Xe fragmentation (Jungclaus) and 238 U projectile fission (Gorska,Pfutzner) –A~110 fission fragment isomers (Bruce) ‘Active Stopper’ campaign I (March 2007) –N=126, 205 Au M4 (Z=82 holes) electron conversion –Beta-delayed spectroscopy, 188,190,192 Ta → 188,190,192 W ‘Active Stopper’ campaign II (July 2007) –N=126 part II (J. Benlliure et al.,) –A~50/60 N=Z decays (Gadea, Rubio, Gelletly & Fujita)

First Results from the Stopped RISING Campaign at GSI: The Mapping of Isomeric Decays in Highly Exotic Nuclei P.H.Regan 1, A.B.Garnsworthy 1,2, S.J.Steer 1, S.Pietri 1, Zs.Podolyák 1, D.Rudolph 3, M.Górska 4, L.Caceres 4,5, E.Werner- Malento 4,6, J.Gerl 4, H.J.Wollersheim 4, F.Becker 4, P.Bednarczyk 4, P.D.Doornenbal 4, H.Geissel 4, H. Grawe 4, J.Grębosz 4,7, R.Hoischen 3, A.Kelic 4, I.Kojouharov 4, N.Kurz 4, F.Montes 4, W.Prokopowicz 4, T.Saito 4, H.Schaffner 4, S.Tashenov 4, A.Heinz 2, M.Pfützner 6, T.Kurtukian-Nieto 8, G.Benzoni 9, M.Hellström 2, A.Jungclaus 5, L.-L.Andersson 3, L.Atanasova 10, D.L.Balabanski 11, M.A.Bentley 12, B.Blank 13, A.Blazhev 14, C.Brandau 1,4, J.Brown 12, A.M.Bruce 15, F.Camera 9, W.N.Catford 1, I.J.Cullen 1, Zs.Dombradi 16, E.Estevez 8, C.Fahlander 3, W.Gelletly 1, G.Ilie 14, E.K.Johansson 3, J.Jolie 14, G.A.Jones 1, M.Kmiecik 7, F.G.Kondev 17, S. Lalkovski 10,15, Z.Liu 1, A.Maj 7, S.Myalski 7, S.Schwertel 18, T.Shizuma 1,19, A.J.Simons 1, P.M.Walker 1, O. Wieland 9 1 Dept. of Physics, University of Surrey, Guildford, GU2 7XH, UK 2 WNSL, Yale University, New Haven, CT , USA 3 Department of Physics, Lund University, S Lund, Sweden 4 GSI, Planckstrasse 1, D-64291, Darmstadt, Germany 5 Departamento de Fisica Teórica, Universidad Autonoma de Madrid, E-28049, Madrid, Spain 6 IEP Warsaw University, Hoźa 69, PL The Henryk Niewodniczański Institute of NuclearPhysics, PL , Kraków, Poland 8 Universidad de Santiago de Compostela, E-15706, Santiago de Compostela, Spain 9 INFN, Universitá degli Studi di Milano, I-20133, Milano, Italy 10 Faculty of Physics, University of Sofia, BG-1164, Bulgaria & The Institute for Nuclear Research, Bulgarian Academy of Science, BG-1784, Sofia, Bulgaria 11 Dipartimento di Fisica, Universit ´a di Camerino, I-62032, Italy 12 Dept. of Physics, University of York, Heslington, York, Y01 5DD, UK 13 CENBG, le Haut Vigneau, Bordeaux, F-33175, Gradignan Cedex, France 14 IKP, Universit¨at zu Köln, D-50937, Köln, Germany 15 School of Engineering, University of Brighton, Brighton, BN2 4GJ, UK 16 Institute for Nuclear Research, Debrecen, H-4001, Hungary 17 Nuclear Engineering Division, Argonne National Laboratory, Argonne IL-60439, USA 18 Physik Department E12, Technische Universität München, Garching, Germany 19 Japan Atomic Energy Agency, Kyoto, , Japan

Workshop on RISING Physics Madrid 6-8 November 2006

Shell structure south of 208 Pb Spokesperson: Zsolt Podolyak, Surrey cold fragmentation of 208 GeV/u main aim: spectroscopy of N=126 isotones 206 Hg, 204 Pt and 202 Os 204 Pt 202 Os See Jeff Tostevin for related reaction theory

Steer, Podolyak et al., to be submitted to PRL

204 Pt populated via 4-proton-knockout from 208 Pb T 1/2 =8.41(16)  s T 1/2 =152(16) ns short isomer: long isomer:

N=126 isotones: (  h 11/2 ) -2,4 I  =10 + isomers 206 Hg Z=80 B. Fornal et al. PRL 87 (2001)  s 1/2 -1 d 3/2 -1  s 1/2 -1 h 11/2 -1  d 3/2 -1 h 11/2 -1  h 11/2 -2 SM 92(8) ns 2.15(21)  s 204 Pt Z=78 152(16) ns 8.41(16)  s  d 3/2 -1 d 5/2 -1  d 5/2 -1 h 11/2 -1 ? Results require modification of SPE and/or interactions ! SM Z. Podolyak, S. Steer et al., PRL, in preparation

205 Au 126 electron conversion!! h 11/2 → d 3/2 M4 transition (half-life a few seconds…..) New single particle (hole) information around 208 Pb core. K L

Fragmentation reaction studies: ‘cold’ (proton removal only) fragmentation (N=126: 206 Hg, 204 Pt) hot fragmentation ( 190 Pb:  =18,  =0!) high-spin states 27ħ in 148 Tb, ( 49 / 2 ) in 147 Gd Z1 Z2 A/Q Pos. at S4 148 Tb Tb E. Werner-Malento, Zs. Podolyak et al. NB: 148 Tb:  = (82-65)=17  =(126-83)= 33 from 208 Pb beam. Highest discrete spin observed to date via rragmentation reaction.

Physics aims of the RISING stopped beam campaign 82 Nb, 86 Tc 54 Ni 130 Cd 204 Pt 106 Zr

Is there evidence for a N=82 shell quenching ? Assumption of a N=82 shell quenching leads to a considerable improvement in the global abundance fit in r-process calculations ! r-process abundances mass number A exp. pronounced shell gap shell structure quenched

Indirect evidence for a N=82 shell quenching ? Kautzsch et al., Eur. Phys. J. A9 (2000) 201 from ß-decay studies at ISOLDE Can the anomalous behaviour of 2 + energies in the Cd isotopes towards N=82 be attributed to a change in the N=82 shell gap ?

g 9/2 Search for the 8 + (g 9/2 ) -2 seniority isomer in 130 Cd two proton holes in the g 9/2 orbit 6-proton-knockout from 136 Xe: A. Jungclaus fission of 238 U: M. Górska, M. Pfützner June/July 2006 M. Górska et al., Phys. Rev. Lett. 79 (1997)

A/q position at S4 S4 position Identification of 130 Cd in the fragmentation of 136 Xe A/q position at S2 S2 position Z= Cd 4000 identified 130 Cd ions in fragmentation (2300 in fission) 750 MeV/u 136 Xe 4 g/cm 2 Be  meas ( 130 Cd)~150 pb

Singles  -spectrum in delayed coincidence with implanted 130 Cd ions T 1/2 =220(30) ns TIME ENERGY

 coincidence spectra Gate: 128 keV Gate: 138 keV Gate: 539 keV Gate: 1325 keV 0+0+ (2 + ) (4 + ) (6 + ) (8 + ) SM 130 Cd Decay of the 8 + isomer in 130 Cd T 1/2 =173nsT 1/2 =220(30)ns New results give no evidence for a N=82 shell quenching ! A. Jungclaus, L. Cáceres et al.,

0+0+ (2 + ) (4 + ) (6 + ) (8 + ) 0+0+ (2 + ) (4 + ) (6 + ) (8 + ) 0+0+ (2 + ) (4 + ) (6 + ) (8 + ) E x (MeV) 76 Ni Cd Cd g 9/2 -2  g 9/ / Unexpected scaling of (g 9/2 ) 2 two-body interaction levels are pure (g 9/2 ) -2 states energy spread scales with A -1 not with ħ  =41· A -1/3 as commonly assumed idea of H. Grawe C. Mazzocchi et al., PLB 622 (2005) 45