Date post: | 29-Dec-2015 |
Category: |
Documents |
Upload: | bertina-mason |
View: | 233 times |
Download: | 2 times |
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’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