Recent Results in Fragmentation Isomer Spectroscopy with RISING

Paddy Regan

Dept. of Physics

University of Surrey

Guildford, GU2 7XH, UK

p.regan@surrey.ac.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’061. N=Z~43 nuclei (107Ag beam, PHR)2. N=126, ‘south’ ( 208Pb beam, Zsolt Podolyák)3. 54Ni/54Fe isospin symmetry (58Ni beam, Dirk Rudolph)

To run in July 2006, • 130Cd isomers (136Xe beam, Andrea Jungclaus)• 130Cd via fission (238U beam, Magda Gorska) • Fission fragments for A~110 (238U beam, Alison Bruce)

‘Active stopper’ expts for 2007 (N~126, 170Dy, Tz=-1.)

primary beamPb @ 1GeV/u

Production target

Central focus, S2Final focus, S4

E(Z2)

cu

eB

Q

A

FTO

catcher

degraderdegrader

dipole, B

scintscint

MW=x,y

scint(veto)

Use FRS@GSI or LISE3@GANIL 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) 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

In-Flight Technique Using Projectile Fragmentation

208Pb beam at 1 GeV/u allows production of ( high-spin isomers,

M. Pfützner et al. Phys Rev. C65 (2002) 064604

High spins (>35/2) populated

CHICO + GS data136Xe + 198Pt

Stopped Rising Array @ GSI: 15 x 7 element CLUSTERsPhotopeak 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 2He

• Deuteron (T=0,S=1) is the only A=2 bound system

Neutrons: Tzn=+1/2

Protons: Tzp=-1/2

Tz=1/2(N-Z)

T=|Tz|

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

62Ga : S.M. Vincent al al., Phys. Lett. 437B (1998) 264 D. Rudolph et al., Phys. Rev. C69 (2004) 034309

66As: R. Grzywacz et al., Nucl. Phys. A682 (2001) 41c R. Grzywacz et al., Phys. Lett. 429B (1998) 247

70Br: M. Karny et al., Phys. Rev. C70 (2004) 014310 D.G. Jenkins et al., Phys. Rev. C65 (2002) 0644307 G. DeAngelis et al., Eur. Phys. J. A12 (2001) 51 74Rb: C.D. O’Leary et al., Phys. Rev. C67 (2003) 021301 D. Rudolph et al., Phys. Rev. Lett. 76 (1996) 376 78Y ? 82Nb ? p3n reactions, -delayed tagging ?

86Tc: C. Chandler et al., Phys. Rev. C61 (2000) 044309

I=0+ T=1 ground states from -decay for 74Rb, 78Y, 82Nb, 86Tc and 90RhJ. Garces Narro et al., Phys. Rev. C63 (2001) 044307T. 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

-2000

-1000

0

1000

2000

3000

4000

0 20 40 60 80 100

A

E(T

=1-T

=0)

(keV

)

T=0 Dominant

T=1Dominant

?

s-d shell8-20

f shell20-28

p-f-g shell28-50

86Tc

E(1st T=1 state) - E(1st T=0 state) in Odd-Odd, N=Z Nuclei

?

From A. Garnsworthy

Heaviest odd-odd, N=Z gammas, isobaric analog states ? GANIL (fragmentation ‘pick up’) 86Tc from 92Mo beam,

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

Nilsson orbitalsLikely configurations

of 86Tc 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

86Tc

Previously Proposed Structure of 86Tc 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) 044307)

• All other information is uncertain

86Mo

From A. Garnsworthy

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

88Zr

S. Pietri et al., 107Ag beam

S. Pietri et al., 107Ag beamRISING Mar’06

I=12+ isomer N. Marginean

et al., PRC67 (2003) 061301

A.B. Garnsworthy et al.,

A.B. Garnsworthy et al.,

The Proposed Structure of 86Tc

850 keVE3 = 8.35x10-6

s

270 keVM2 = 1.1x10-6 s

581 keVM1 = 3.1x10-14

sA.B. Garnsworthy et al., preliminary

l, j=3 ?g9/2 x p3/2

SM calcs by H. Grawe (GSI)

New Data point

-2000

-1000

0

1000

2000

3000

4000

0 20 40 60 80 100

A

E(T

=1-T

=0)

(keV

)

T=0 Dominant

T=1 More Competitive

40Ca

16O

56Ni

86Tc

The Trend Continues?!?

E(2+) for odd-odd N=Z T=1 states follows e-e trend with2

86Tc74Rb

70Br66As

62Ga

208Pb region SUPER-FRS Yields

many μs isomersexpected

212Po, 18+, 65s

215Ra, 43/2-, 800ns

217Ac, 29/2+, 1μs

N=126, holes in 208Pb

Gamma-gamma analysis on 200Pt 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) 212501

• 206Hg (Z=80) is the most ‘neutron-rich’ N=126even-even isotope withstructural information todate….how robust is theN=126 shell ?

• Look at isomeric B(M) for seniority isomers basedon proton (h11/2)-n states.

206Hg isomers, N=126, S. Steer, Zs. Podolyak et al., 208Pb 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 knockoutfrom h11/2 orbitals. (< 100 ns half-life).

S. Steer, Zs. Podolyak et al., 208Pb fragmentation, RISING Mar’06

New isomer in 204Pt !! 4 proton holes in 208Pb double magic closed shell !!

S. Steer, Zs. Podolyak et al., 208Pb fragmentationRISING Mar’06

Podolyàk, Steer et al., 208Pb frag. RISING @ GSI Mar’06

N=126, 4 proton holes

March’06RISINGdata

See Mike Bentley’s talk for more details on this ‘beauty!’

54Ni 10+ isomer (mirror of 54Fe)…..proton activity…..

D. Rudolph et al., 58Ni fragmentation RISING Mar.’ 06

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