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Opportunities for Spectroscopy of super heavy elements. Overview. In-beam Spectroscopy of SHE is a very successful technique Complementary to Decay Studies Optical Studies. Scientific Goals. Single Particle structure of SHE Detailled in-beam spectroscopy of nuclei - PowerPoint PPT Presentation
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EURISOL Workshop 16-20 Jan 2006EURISOL Workshop 16-20 Jan 2006 R-D HerzbergR-D Herzberg
Opportunities for Opportunities for Spectroscopy of super heavy Spectroscopy of super heavy
elementselements
OverviewOverview
In-beam Spectroscopy of SHE is a In-beam Spectroscopy of SHE is a very successful techniquevery successful technique
Complementary to Decay StudiesComplementary to Decay Studies
Optical Studies Optical Studies
Scientific GoalsScientific Goals Single Particle structure of SHESingle Particle structure of SHE
Detailled in-beam spectroscopy of nuclei Detailled in-beam spectroscopy of nuclei
from Cf to Ds and beyondfrom Cf to Ds and beyond
Anchor “floating” chainsAnchor “floating” chains
Ideally follow the stability line…Ideally follow the stability line…
… … or at least stay as close to it as possible.or at least stay as close to it as possible.
Deformation brings strongly downsloping orbitals from above the next spherical shell gap close to the Fermi surface.
Nobelium region is ideal for this:
“Large” Cross sect.
f5/2 - f7/2 probed
Systematics possible
Why study Why study transfermiums?transfermiums?
Magic ShellsMagic Shells
M Bender et al, PLB
Decay StudiesDecay Studies Important for ground state properties:Important for ground state properties:
Mass (Mass (≠ ≠ Q-value)Q-value) Spin + ParitySpin + Parity Decay modesDecay modes LifetimeLifetime ShapeShape
Confirmation of chainsConfirmation of chains Unambiguous (Z,N) identificationUnambiguous (Z,N) identification
S. Hofmann, Nucl. Phys. News Intl
108110
112
114
120
109 RIB on Pb/Bi
3·109 132Sn onvarious targets
The SHE reach of MAFF
S. Hofmann, Nucl. Phys. News 14, 5 (2004)
108110
112
114
120
109 RIB on Pb/Bi
3·109 132Sn onvarious targets
The SHE reach of MAFF
S. Hofmann, Nucl. Phys. News 14, 5 (2004)
108110
112
114
120
109 RIB on Pb/Bi
3·109 132Sn onvarious targets
The SHE reach of MAFF
S. Hofmann, Nucl. Phys. News 14, 5 (2004)
108110
112
114
120
109 RIB on Pb/Bi
3·109 132Sn onvarious targets
The SHE reach of MAFF
S. Hofmann, Nucl. Phys. News 14, 5 (2004)
108110
112
114
120
-7 MeV
-6 MeV
-5 MeV
-4 MeV
-3 MeV
Shell-CorrectionEnergies
R. Smolanczuk et al.,Phys. Rev. C 52, 1872(1995)
R. Smolanczuk and A. Sobiczewski,Proc. XV Nucl. Phys. Div. Conf., Singapore (1995), p. 313
3·109 132Sn onvarious targets
In-beam StudiesIn-beam Studies
Experience with gamma and CE studiesExperience with gamma and CE studies Unique set of problemsUnique set of problems Main challenge is Fission Main challenge is Fission
251251MdMd
B(M1)/B(E2) B(M1)/B(E2) K K22(g(gKK-g-gRR))22/Q/Q0022
gK ~ 0.7 Mainly E2[514]7-
2
7 -
2
1 -
2
[521] 1-
2a ~ 0.9:
Mainly E2
7 +
2
[633]7+
2gK ~ 1.3 Mainly M1
E2
M1
C. Theisen priv comm.
251251MdMd
First rotationalFirst rotational
band firmly band firmly
establishedestablished
in an odd in an odd
transfermiumtransfermium
nucleusnucleus
C. Theisen/A Chatillon priv comm.
MoI 2MoI 2
A. Afanasiev, PRC 67, 24309, (2002)
IsomersIsomers
Provide information on quasiparticle Provide information on quasiparticle statesstates
Indirect evidence for isomer in Indirect evidence for isomer in 254254NoNo
seen in the 1970sseen in the 1970s
A. Ghiorso et al, PRC 7 (1973) 2032A. Ghiorso et al, PRC 7 (1973) 2032
Several searches in JYFL and ANLSeveral searches in JYFL and ANL
Isomer TaggingIsomer Tagging
γ
α
γγ
Jurogam Array
Target Chamber
DSSD Pixel
e
Prompt Gammas
Isomer decay
Followed by
Alpha decay
•Use the DSSD as a calorimeter! GD Jones, NIM A488, 471 (2002)
InterpretationInterpretation
1.4 266 ms
(8-)
0+
2.6 184 ms
Experiment
Which Cases?Which Cases?
Neutron Number
Pro
ton N
um
ber
Already Done
PotentiallyDoable
Feasibility dependsOn the specifics in
Each and every case!
How to get there?How to get there?
Available Targets:Available Targets: 208208Pb, Pb, 209209Bi (Cold fusion)Bi (Cold fusion) 232232Th, Th, 238238U, U, 243243Am, Am, 248248CmCm (Hot Fusion) (Hot Fusion)
Beams: Far out.Beams: Far out.
Up, up and awayUp, up and away
Picture from S. Hofmann
53K
59Sc
63V
67Mn
73Co
208Pb + X
72Fe
66Cr
62Ti
58Ca
52Ar
209Bi + X
45Cl
39P
35Al
31Na
25F
238U + X
Start from the beam: Start from the beam: 132132SnSnX + 132Sn
N=82
PromisingPromising
The combination of N=82 targets and The combination of N=82 targets and doubly magic doubly magic 132132Sn should be Sn should be favourable.favourable.
Unfortunately they have the highest Unfortunately they have the highest Coulomb barriers Coulomb barriers
Lots of angular momentum Lots of angular momentum
Egido & Robledo PRL 85 1198
92Kr + 164Dy 256No*
Ex = 24 MeV
High spin states in High spin states in SHESHE
48Ca + 208Pb 256No*
Ex = 21 MeV
Nuclear IdentificationNuclear Identification
Alpha tagging Alpha tagging Easy, uniqueEasy, unique
Beta TaggingBeta Tagging Tricky, need gammaTricky, need gamma
Fission TaggingFission Tagging Easy, not uniqueEasy, not unique
Isomer TaggingIsomer Tagging Low Efficiency, Low Efficiency, UniqueUnique
EquipmentEquipment
Target Target High beam quality neededHigh beam quality needed Prompt Spectrometer capable of high ratePrompt Spectrometer capable of high rate
EXOGAM, AGATAEXOGAM, AGATA Separator with large transmissionSeparator with large transmission
gas-filled Separator needed for EURISOLgas-filled Separator needed for EURISOL Excellent Recoil IDExcellent Recoil ID DAQ capable of high rate: DAQ capable of high rate: Triggerless, Digital Triggerless, Digital
Gamma Ray SpectrometerGamma Ray Spectrometer
Dominant channel is constant ~0.1 - 1b Dominant channel is constant ~0.1 - 1b Fission. This limits Ge rate!Fission. This limits Ge rate!
Target wheel spokes need beam Target wheel spokes need beam sweepingsweeping
High granularity and large distance to High granularity and large distance to keep individual rates low keep individual rates low (AGATA!)(AGATA!)
Background from entrance windows etc.Background from entrance windows etc. Need windowless system!Need windowless system!
AGATAAGATA((AAdvanced dvanced GAGAmma mma TTracking racking AArray)rray)
4 4 -array -array for Nuclear Physics Experiments at European for Nuclear Physics Experiments at European accelerators providing radioactive and high-intensity stable accelerators providing radioactive and high-intensity stable
beamsbeams
Main features of AGATA
Efficiency: 40% (M =1) 25% (M =30)today’s arrays ~10% (gain ~4) 5% (gain ~1000)
Peak/Total: 55% (M=1) 45%
(M=30)today ~55% 40%
Angular Resolution: ~1º FWHM (1 MeV, v/c=50%) ~ 6 keV !!!today ~40 keV
Rates: 3 MHz (M=1) 300 kHz (M
=30)today 1 MHz 20 kHz
• 180 large volume 36-fold segmented Ge crystals in 60 triple-clusters • Digital electronics and sophisticated Pulse Shape Analysis algorithms allow• Operation of Ge detectors in position sensitive mode -ray tracking
Electron SpectrometerElectron Spectrometer
Fission does not readily produce CEFission does not readily produce CE SHE produce more CE than Gamma SHE produce more CE than Gamma
Delta electrons require HV barrierDelta electrons require HV barrier Generally difficultGenerally difficult Rate concentrated near field axisRate concentrated near field axis Baseline dirty -> need digital cardsBaseline dirty -> need digital cards
SACREDSACRED
At present, electron experimentsUse 20% of the beam current of Gamma experiments.
Rate adjustable with HV barrier.
Targets need to be thinner (0.25 mg/cm2)
P.A. Butler et al., NIM A 381, 433 (1996)
H. Kankanpaa et al., NIM A 534, 503 (2004)
SAGESAGE
Fermium Wins Heavyweight Title
IP
E [cm-1]
Excimer
Laser
l=351 +
353 nmDye Laser
l=398 nm0
52400
25100
ScanRegion
5I6o
3H6o
5G5o
3G5o
3I7o
J =
• Observation and Assignment of Atomic Levels without any Previous Knowledge of the Atomic Structure
• Demonstrated with a Sample of 1010 Atoms 255Fm, t1/2= 20.1 h, Produced at the HFIR, Oak Ridge
• Based on State-of-the-Art MCDF Calculations
25 April 2003
MCDF Calculation
Experiment
Laser
SHIPZ=102
Resonance Ionization Spectroscopyat Trans-Fermium Elements
BufferGasCell
GSIMAFF
@
Sewtz et al., Phys. Rev. Lett., 90 (2003) 163002-1
o
oDetermination of
• the Valence Electron Configuration by Ion Mobility Measurements ~ eV
• Atomic Levels / Ionization Potentials by Optical Spectroscopy ~ meV
@ MLLTRAPSHIPTRAP
Determination of the Atomic Structure of the Heaviest Elements M. Sewtz, et al.
Relativistic Effects :
• Contraction of the s1/2, p1/2 Orbitals
• Expansion of the d,f Orbitals
Variations in Atomic and Chemical Properties
J.P. Desclaux At. Data Nucl. Data Tables 12, 311 (1973)
Sewtz et al., Spectrochim. Acta B 58, 1077 (2003) ( )
ConclusionsConclusions
In-beam studies will need to be assessed In-beam studies will need to be assessed individually but will be possibleindividually but will be possible
Decay Spectroscopy is vital Decay Spectroscopy is vital
Optical Spectroscopy provides Optical Spectroscopy provides complementary informationcomplementary information
Exciting Times!Exciting Times!