First Results from the Stopped RISING Campaign at GSI: The Mapping of Isomeric Decays in Highly Exotic Nuclei Paddy Regan (for the Stopped Beam Rising Collaboration) Dept. of Physics, University of Surrey Guildford, Surrey, GU2 7XH, UK p.regan@surrey.ac.uk

RISING = Rare ISotope INvestigations at GSI 3 major ‘campaigns’ so far using 15 EUROBALL Clover germanium dets. 1) ‘Fast’ (in-beam) Campaign 2) gRISING Campaign 3) ‘Stopped’ (isomer) Campaign

Projectile Fragmentation Reaction Process Reaction Products still travelling at Relativistic Energies Beam at Relativistic Energy ~0.5-1 GeV/A FIREBALL Formation of a compound nucleus Target Nucleus Abrasion Ablation

Use FRS@GSI or LISE3@GANIL to ID nuclei. In-Flight Technique Using Projectile Fragmentation Production target Central focus, S2 Final focus, S4 primary beam Pb @ 1GeV/u dipole, B degrader degrader MW=x,y scint scint catcher E(Z2) Use FRS@GSI or LISE3@GANIL to ID nuclei. Transport some in isomeric states (TOF~ x00ns). Stop and correlate isomeric decays with nuclei id. scint (veto) eg. R. Grzywacz et al. Phys. Rev. C55 (1997) p1126 ⇨ LISE C. Chandler et al. Phys. Rev. C61 (2000) 044309 ⇨ LISE M. Pfützner et al. Phys. Lett. B444 (1998) p32 ⇨ FRS Zs. Podolyak et al. Phys. Lett. B491 (2000) p225 ⇨ FRS M. Pfützner et al. Phys Rev. C65 (2002) 064604 ⇨ FRS M. Caamano et al., Eur.Phys. J. A23 (2005) p201 ⇨ FRS

82Nb 73Kr Blank and Regan, Physics World Jan. 2000 92Mo@ GANIL Produce many exotic nuclei: Stopped them to study both 1) Isomer decays (10ns-1ms) 2) Beta decays (20ms - 10s)

Stopped Rising Array @ GSI: 15 x 7 element CLUSTERs Photopeak efficiency ~10% at 1.3 MeV. XIA-DGF electronics see S. Pietri et al., NIM B (2007) in press, Acta Phys. Pol. (2007) in press)

S. Pietri et al., Acta Phys. Pol. B (2007), in press

Physics aims and regions for the Stopped RISING Campaigns (2006)

What is an isomer ? Metastable (long-lived) nuclear excited state. ‘Long-lived’ could mean ~10-19 seconds, shape isomers in a-cluster resonances or ~1015 years 180Ta 9-->1+ decay. Why/when do you get isomers? (i) large change in spin (‘spin-trap’) (ii) small transition energy between states (seniority isomers) (iii) dramatic change in structure/shape (fission isomers) and/or underlying symmetry (K-isomers) What do isomers tell you ? Isomers occur due to single particle structure. Transitions are hindered between states with very different structures (note, this is not case for seniority isomers).

From P.M.Walker and G.D.Dracoulis, Physics World Feb. 1994

74Kr, shape isomer a-decay to states in 208Pb. 212Po, high-spin a-decaying yrast trap. (also proton decaying isomers, e.g, 53Co PLB33 (1970) 281ff. E0 (ec) decay High-spin, yrast-trap (E3) in 212Fr K-isomer in 178Hf

Fragmentation of 600 MeV/A 58Ni beam (D.Rudolph et al.) Main Aim: Observe Ip=10+ isomer in 54Ni (Isomer already known in mirror, 54Fe) 82Nb n=z=41

D. Rudolph et al., RISING, Feb/Mar'06

54Ni 10+ isomer (Mirror of 54Fe) D. Rudolph et al., 58Ni fragmentation 451 145 1226 1392 New Line New Line - 1327 keV 3240 3385

γγ Coincidence Spectra D. Rudolph et al.,

But….where is the 1327 keV line ? D. Rudolph et al., RISING, Feb/Mar'06

Isomer proton radioactivity from Ip=10+ isomer in 54Ni !! D. Rudolph et al., RISING, Feb/Mar'06

Dirk Rudolph et al., Feb/Mar ’06 RISING

Z. Janas et al., Phys. Rev. Lett. 82 (1999) 295 N=Z crossed proton drip line around A~80

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

T=1: Ip=0+ New Data point T=0 : Ip=1+or (2j)+ ?

Number of levels below 1 MeV in odd-odd nuclei np T=1 pairing gap ? np T=0 pairing…. Low-lying Ip=1+ states expected… is there any evidence ? ‘yrastness’ problem in well deformed systems… D.G. Jenkins, et.al. Phys. Rev. C65, 064307 (2002)

C. Chandler et al.,

A.B. Garnsworthy et al.,

A.B. Garnsworthy et al.,

A.B. Garnsworthy et al.,

Z=43, Tc

Isomeric decays in both 82Nb and 86Tc appear to be E2 from both internal conversion and lifetime evaluations…. Isomer spins then assumed to be Ip=6+? but what configurations...?

82Nb b 86Tc

C. Chandler et al. 7/2 + x 5/2+ = 6+ ?

Triaxial deformation causes a reordering of ~’Nilsson’ levels….

C. Chandler et al., Phys. Rev. C61 (2000) 044309

204Pt: N=126 130Cd: N=82

Fragmentation of 1 GeV/A 208Pb beam Zs. Podolyák et al. Main Aim: Spectroscopy of N=126 nuclei: 206Hg, 204Pt, 202Os Additional: New isomeric decays in 203Pt, 189Ta, 204Au,… Reaction studies: 148Tb I=27+; 147Gd I=(49/2) 190Pb (hot fragmentation) 204Pt (cold fragmentation) 82Nb n=z=41

I=10+ isomer, 2 proton cold knockout from h11/2 orbitals. (< 100 ns half-life). S. Steer, Zs. Podolyak et al., 208Pb fragmentation, RISING Mar’06

S.J. Steer, Zs. Podolyak et al.,

S.J. Steer, Zs. Podolyak et al.,

N=126 isotones: (ph11/2)-2,4 Ip=10+ isomers. Z=80, 206Hg Z=78, 204Pt

S.J. Steer, Zs. Podolyak, B.A. Brown et al.,

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

Summary Experimental data from 2006 passive stopper experiments N~Z isomers, isospin symmetry/pairing studies around 56Ni (Dirk Rudolph) and highly deformed A~80 regions. N~126, high spins (148Tb), K-isomers (190W)…(Zsolt Podolyak) Reaction mechanism studies of ‘cold knockout’ to (ph11/2)-2, Ip=10+ seniority isomers (Jeff Tostevin et al.,) Neutron-rich ~132Sn nuclei with 136Xe fragmentation (Andrea Jungclaus) and 238U projectile fission (Magda Gorska/Marek Pfuztner) under analysis. r-process path isomers A~110 fission fragment isomers (Alison Bruce) ‘Active Stopper’ campaign (2007) 3 x 5cm x 5cm DSSSD: correlated b-delayed gammas… N~126 neutron-rich to 170Dy valence max. (March 2007)

First Results from the Stopped RISING Campaign at GSI: The Mapping of Isomeric Decays in Highly Exotic Nuclei P.H.Regan1, A.B.Garnsworthy1,2, S.J.Steer1, S.Pietri1, Zs.Podolyák1, D.Rudolph3, M.Górska4, L.Caceres4,5, E.Werner-Malento4,6, J.Gerl4, H.J.Wollersheim4, F.Becker4, P.Bednarczyk4, P.D.Doornenbal4, H.Geissel4, H. Grawe4, J.Grębosz4,7, R.Hoischen3, A.Kelic4, I.Kojouharov4, N.Kurz4, F.Montes4, W.Prokopowicz4, T.Saito4, H.Schaffner4, S.Tashenov4, A.Heinz2, M.Pfützner6, T.Kurtukian-Nieto8, G.Benzoni9, M.Hellström2, A.Jungclaus5, L.-L.Andersson3, L.Atanasova10, D.L.Balabanski11, M.A.Bentley12, B.Blank13, A.Blazhev14, C.Brandau1,4, J.Brown12, A.M.Bruce15, F.Camera9, W.N.Catford1, I.J.Cullen1, Zs.Dombradi16, E.Estevez8, C.Fahlander3, W.Gelletly1, G.Ilie14, E.K.Johansson3, J.Jolie14, G.A.Jones1, M.Kmiecik7, F.G.Kondev17, S. Lalkovski10,15, Z.Liu1, A.Maj7, S.Myalski7, S.Schwertel18, T.Shizuma1,19, A.J.Simons1, P.M.Walker1, O. Wieland9 1Dept. of Physics, University of Surrey, Guildford, GU2 7XH, UK 2WNSL, Yale University, New Haven, CT 06520-8124, USA 3Department of Physics, Lund University, S-22100 Lund, Sweden 4GSI, Planckstrasse 1, D-64291, Darmstadt, Germany 5Departamento de Fisica Teórica, Universidad Autonoma de Madrid, E-28049, Madrid, Spain 6IEP Warsaw University, Hoźa 69, PL-00-681 7The Henryk Niewodniczański Institute of NuclearPhysics, PL-31-342, Kraków, Poland 8Universidad de Santiago de Compostela, E-15706, Santiago de Compostela, Spain 9INFN, Universitá degli Studi di Milano, I-20133, Milano, Italy 10Faculty of Physics, University of Sofia, BG-1164, Bulgaria & The Institute for Nuclear Research, Bulgarian Academy of Science, BG-1784, Sofia, Bulgaria 11Dipartimento di Fisica, Universit ´a di Camerino, I-62032, Italy 12Dept. of Physics, University of York, Heslington, York, Y01 5DD, UK 13CENBG, le Haut Vigneau, Bordeaux, F-33175, Gradignan Cedex, France 14IKP, Universit¨at zu Köln, D-50937, Köln, Germany 15School of Engineering, University of Brighton, Brighton, BN2 4GJ, UK 16Institute for Nuclear Research, Debrecen, H-4001, Hungary 17Nuclear Engineering Division, Argonne National Laboratory, Argonne IL-60439, USA 18Physik Department E12, Technische Universität München, Garching, Germany 19Japan Atomic Energy Agency, Kyoto, 619-0215, Japan

(pg9/2)-2,4I=14 + (ng9/2)-2,4I=14+ (pg9/2)-2I=8+ + (ng9/2)-2I=8+ + Can use known isomers with 100% cascade decays to cive detector response over full energy range….

High granularity of RISING reduces ‘prompt flash’ problems…. 7/105… DGF timing of flash, comparable to former ‘analog’ timing. S. Pietri et al., RISING Feb/Mar. '06