Recent Results in Fragmentation Isomer Spectroscopy with RISING Paddy Regan Dept. of Physics University of Surrey Guildford, GU2 7XH, UK

Major campaign using ‘retired EUROBALL’ cluster detectors for fragmentation-based nuclear spectroscopy. Stopped-Beam Campaign to study decays from isomers and following beta-decay. Three experiments for ‘isomer only’ part ran in Feb/Mar’06 1. N=Z~43 nuclei ( 107 Ag beam, PHR) 2.N=126, ‘south’ ( 208 Pb beam, Zsolt Podolyák) 3.54Ni/54Fe isospin symmetry ( 58 Ni beam, Dirk Rudolph) To run in July 2006, 130 Cd isomers ( 136 Xe beam, Andrea Jungclaus) 130 Cd via fission ( 238 U beam, Magda Gorska) Fission fragments for A~110 ( 238 U beam, Alison Bruce) ‘Active stopper’ expts for 2007 (N~126, 170 Dy, Tz=-1.)

primary beam 1GeV/u Production target Central focus, S2 Final focus, S4  E(Z 2 ) catcher degrader dipole, B  scint MW=x,y scint (veto) Use or to ID nuclei. Transport some in isomeric states (TOF~ x00ns). Stop and correlate isomeric decays with nuclei id. eg. R. Grzywacz et al. Phys. Rev. C55 (1997) p1126 ⇨ LISE C.Chandler et al. Phys. Rev. C61 (2000) ⇨ 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) ⇨ FRS M. Caamano et al., Eur.Phys. J. A23 (2005) p201 ⇨ FRS In-Flight Technique Using Projectile Fragmentation

208 Pb beam at 1 GeV/u allows production of ( high-spin isomers, M. Pfützner et al. Phys Rev. C65 (2002) High spins (>35/2) populated

CHICO + GS data 136 Xe Pt

Stopped Rising GSI: 15 x 7 element CLUSTERs Photopeak efficiency 15-17% at 1.3 MeV

Isospin Protons and Neutrons are 2 states of the same particle Pauli principle prevents T=0 states for nn and 2 He Deuteron (T=0,S=1) is the only A=2 bound system Neutrons:T zn =+1/2 Protons:T zp =-1/2 T z =1/2(N-Z) T=|T z | Adapted from R.Casten, Nuclear Structure from a Simple Perspective (2000)

Long standing problem…. studies of N=Z nuclei and T=0, T=1 competition. One can obtain spectroscopic info. from isomeric states

62 Ga : S.M. Vincent al al., Phys. Lett. 437B (1998) 264 D. Rudolph et al., Phys. Rev. C69 (2004) As: R. Grzywacz et al., Nucl. Phys. A682 (2001) 41c R. Grzywacz et al., Phys. Lett. 429B (1998) Br: M. Karny et al., Phys. Rev. C70 (2004) D.G. Jenkins et al., Phys. Rev. C65 (2002) G. DeAngelis et al., Eur. Phys. J. A12 (2001) Rb: C.D. O’Leary et al., Phys. Rev. C67 (2003) D. Rudolph et al., Phys. Rev. Lett. 76 (1996) Y ? 82 Nb ? p3n reactions,  -delayed tagging ? 86 Tc: C. Chandler et al., Phys. Rev. C61 (2000) I  =0 + T=1 ground states from  -decay for 74 Rb, 78 Y, 82 Nb, 86 Tc and 90 Rh J. Garces Narro et al., Phys. Rev. C63 (2001) T. Faestermann et al., Eur. Phys. J. A15 (2002) 185 Summary of odd-odd N=Z Spectroscopy (to Mar. 06)

T=0,1 Competition in N=Z nuclei Spins of the GS in odd-odd N=Z nuclei can help identify which mode is dominant With increasing mass there is competition between T=0 and T=1 collective modes From A. Garnsworthy

Heaviest odd-odd, N=Z gammas, isobaric analog states ? GANIL (fragmentation ‘pick up’) 86 Tc from 92 Mo beam, C. Chandler et al. Phys. Rev. C61 (2000)

Nilsson orbitals Likely configurations of 86 Tc  s isomer Both  and in either/or 5/2 + [422] or 5/2 - [303] This would give the isomer spin 5 + (or perhaps 5 - ?) Would not likely decay by to the T=1 4 + due to selection rule for E1 between T=0 and T=1 states. From A. Garnsworthy

86 Tc Previously Proposed Structure of 86 Tc from GANIL expt. data Ground state spin assignment inferred through Fermi super allowed β-decay half life (see J Garces Narro et.al., Phys. Rev. C 63 (2001) ) All other information is uncertain 86 Mo From A. Garnsworthy

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

88 Zr S. Pietri et al., 107 Ag beam

RISING Mar’06 I  =12 + isomer N. Marginean et al., PRC67 (2003)

A.B. Garnsworthy et al.,

The Proposed Structure of 86 Tc 850 keV E3 = 8.35x10 -6 s 270 keV M2 = 1.1x10 -6 s 581 keV M1 = 3.1x s A.B. Garnsworthy et al., preliminary  l,  j=3 ? g 9/2 x p 3/2

SM calcs by H. Grawe (GSI)

New Data point

E(2 + ) for odd-odd N=Z T=1 states follows e-e trend with  2 86 Tc 74 Rb 70 Br 66 As 62 Ga

208 Pb region SUPER-FRS Yields many μs isomers expected 212 Po, 18 +, 65s 215 Ra, 43/2 -, 800ns 217 Ac, 29/2 +, 1μs N=126, holes in 208 Pb

Gamma-gamma analysis on 200 Pt isomer (21 ns!), M. Caamano et al. Nucl. Phys. A682 (2001) p223c; Acta Phys. Pol. B32 (2001) p763 stripping effect to extend lifetime

B. Fornal et al., Phys. Rev. Lett. 87 (2001) Hg (Z=80) is the most ‘neutron-rich’ N=126 even-even isotope with structural information to date….how robust is the N=126 shell ? Look at isomeric B(M ) for seniority isomers based on proton (h 11/2 ) -n states.

206 Hg isomers, N=126, S. Steer, Zs. Podolyak et al., 208 Pb RISING 5 - isomer 10 + isomer Relative isomeric ratios give insight into cold proton ‘knockout’ theory see J. Tostevin AIP Conf. Proc. 819 (2006) p523.

I  =10 + isomer, 2 proton cold knockout from h 11/2 orbitals. (< 100 ns half-life). S. Steer, Zs. Podolyak et al., 208 Pb fragmentation, RISING Mar’06

New isomer in 204 Pt !! 4 proton holes in 208 Pb double magic closed shell !! S. Steer, Zs. Podolyak et al., 208 Pb fragmentation RISING Mar’06

Podolyàk, Steer et al., 208 Pb frag. GSI Mar’06 N=126, 4 proton holes March’06 RISING data

See Mike Bentley’s talk for more details on this ‘beauty!’ 54 Ni 10 + isomer (mirror of 54 Fe)…..proton activity….. D. Rudolph et al., 58 Ni fragmentation RISING Mar.’ 06

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