Recent spectroscopic results near the Z=100, N=152 Closed Shells Darek Seweryniak Argonne National Laboratory
Recent spectroscopic results near the Z=100, N=152 Closed Shells
Darek Seweryniak Argonne National Laboratory
Interational Symposium on Super Heavy Nuclei 2015, Texas A&M 2
Outline
§ Spectroscopy around deformed magic numbers Z=100, N=152 § Entry point distribu=on in 254No
– direct measurement of the fission barrier § Discovery of two-‐ and four-‐quasipar=cle isomers in 254Rf
– Fission hindrance in K-‐isomers § Outlook
– Argonne Gas-‐Filled Analyzer (AGFA)
3
neutron number
111
112
113
114
117
115
118
116
160 162
164 166 168 170 172 174
176 178 180 182 184
152 158156154
Mt 266
Db 262 Db 263
Sg 266
Db 258Db 256 Db 260Db 257
Rf 260 Rf 261 Rf 262 Rf 263Rf 259Rf 256Rf 255 Rf 258
Bh 261 Bh 262
Rf 257
Db 261
Sg 260 Sg 261 Sg 263Sg 259
Bh 264
Bh
Hs
Ds
Sg 258
Lr 259
No 258
Lr 260
No 259
Lr 261 Lr 262
No 262No 260
Lr 258
No 257
Lr 255
No 254
Lr 254
No 253
Lr 257
No 256
Lr 256
No 255
Md 257
Fm 256
Md 258
Fm 257
Md 259 Md 260
Fm 258 Fm 259
Md 256
Fm 255
Md 253
Fm 252
Md 252
Fm 251
Md 255
Fm 254
Md 254
Fm 253
Es 255 Es 256Es 254Es 251Es 250 Es 253Es 252
Cf 255 Cf 256Cf 253Cf 250Cf 249 Cf 251 Cf 252 Cf 254
110/273110/271
111/272
CHART OF THE NUCLIDES
No
Md
Fm
Es
Cf
prot
on n
umbe
r
150
Db
Rf
Lr
No
Md
Fm
Es
Cf
Z = 114
108Hs 267Hs 265Hs 264
a
a
a
a
a
a
110/270
Hs 266
Sg 262
112/285
9.1539 s
Z/A
T1/2
E (MeV)α
110/269
Mt 268
α
EC
β-‐
SF
112/277
110/267
MtHs 269 Hs 270
Sg 265
Sg
a
aa
a
a
a
a
a
a
a
a
a
a
a
a a
a
aa
aa
108/275
110/279
106/271
112/284112/282
114/286 114/287
10.01
114/288
9.95
116/290
115/288115/287
113/284113/283
111/280
109/276
107/272
111/279
109/2 57
116/291
10.85 10.74
112/285
110/281
114/289
9.82
9.169.54
9.30
8.53
10.00
10.4610.59
10.12
9.75
9.71
9.02
10.37
10.33
105/268
15 ms
32 ms 87 m s
6.3 m s
0.1 s
0.15 s
0.17 s
0.72 s
9.8 s
16 h
9.7 m s
0.48 s
0.1 s0.5 m s
3.6 s
0.18 s
2.4 m in
9.6 s
34 s
0.56 s 0.63 s 2.7 s0.16 s10.20
112/2834.0 s
a
116/292
10.6616 ms
107/2 17
116/29353 ms
1.8 ms118/294
11.65
105/267
1.2 h
10.53
9.70
104/268104/2672.3 h
48 238 249Ca + U.... Cf
208 50 70Pb + Ti.... Zn
Chart courtesy of Y. Oganessian
Cold fusion with
208Pb, 209Bi targets GSI, LBNL, Riken
Hot fusion with 48Ca beams Dubna/LLNL,GSI, LBNL
Super-Heavy Nuclei
In-beam, K-isomers, α-decay fine structure near the deformed Z=100, N=152 shell gaps ANL, Dubna, GSI, JYFL, LBNL
Deformation landscape
Interational Symposium on Super Heavy Nuclei 2015, Texas A&M 4
Minimization of energy by variation of βλ (λ=2-8) generates energy gaps: Z=100 and N=152
Constant prolate deformation ~β2=0.25
Proton and neutron single-particle energies Woods-Saxon potential
R. Chasman et al., Rev. Mod. Phys. 49, 833 (1977) Intera=onal Symposium on Super Heavy Nuclei 2015, Texas A&M
5
protons neutrons
Recoil-Decay Tagging
Implant-decay spatial and time correlations in the DSSD
Q Q Q Q B
E E
e
Fragment Mass Analyzer
Target
Beam
PPAC
160X160 DSSD E,t
M/Q Mass slits
sf
γ
4 clover HPGe
X-array
α sf
2qp
4qp
e γgs
e γ
γ rays and conversion electrons deexciting isomers followed by gs α or sf decay
Interational Symposium on Super Heavy Nuclei 2015, Texas A&M 6
GAMMASPHERE
HPGe
γ
160X160 64mmX64mm DSSD X-Array
5 clovers in box geometry
Fragment Mass Analyzer
8
Compton suppressed HPGe detectors
Interational Symposium on Super Heavy Nuclei 2015, Texas A&M
• typically ~100 HPGe detectors • BGO Compton suppression shields • Double-D segmented detectors at 90o
• Energy resolution 2.5 keV at 1.3 MeV • Efficiency ~10% at 1.3 MeV • since 2003 at ANL • Digital electronics
γ-‐ray energy sum – excita=on energy γ-‐ray mul=plicity – total spin
Gamma-ray calorimetry in 254No
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Determination of fission barrier from HK distribution
Interational Symposium on Super Heavy Nuclei 2015, Texas A&M 10
E*
I
Bf
Sn
γ
E*
I
Bf
Sn
γ
yrast line
yrast line
n n
Fission quickly dominates γ decay just above barrier (~0.5 MeV)
254No HK-entry distributions
Intera=onal Symposium on Super Heavy Nuclei 2015, Texas A&M
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220Th
254No 219 MeV 254No 223 MeV
GS+FMA
Bf(0)=6.6(0.9) MeV, Jsaddle=125(60) h2/MeV from fit between spins 11-‐21
DFT with Gogny D1S and Skyrme interac=ons predict between 6 and 9.6 MeV Microscopic-‐Macroscopic model 6.8 MeV
E1/2-‐Esaddle is 1 MeV at 0h and 0 MeV at 15-‐25h (sta=s=cal calcula=ons)
Esaddle=Bf(0)+I(I+1)/(2*Jsaddle)
254Rf collaboration
Interational Symposium on Super Heavy Nuclei 2015, Texas A&M 12
H.M. David1, J. Chen1, D.S. , F.G. Kondev1, J. Gates7, K. Gregorich7, I. Ahmad1, M. Albers1, M. Alcorta1, B. Back1, B. Baartman7, P. Bertone1, L. Bernstein9, C. Campbell7, M.P. Carpenter1, C.J. Chiara10, M. Chromaz7, R. Clark7, D.T. Doherty2, G. Dracoulis8, N. Esker7, O. Gothe7, J.P. Greene1, P.T. Greenlees3, D.J. Hartley4, K. Hauschild5, P. Fallon7, C.R. Hoffman1, S.S. Hota6, R.V.F. Janssens1, J. Karwsik7, T.L. Khoo1, J. Konki3, T. Lauritsen1, A. Macchiavelli7, P. Mudder7, C. Nair1, Y. Qiu6, J. Rissanen7, A.M. Rogers1, P. Ruotsalainen3, G. Savard1, S. Stolze3, A. Wiens7, S. Zhu1
1Argonne National Laboratory, Argonne, Illinois, USA 2University of Edinburgh, Edinburgh, United Kingdom 3Department of Physics, University of Jyväskylä, Finland 4United States Naval Academy, Annapolis, Maryland, USA 5CSNSM, IN2P3-CNRS, Orsay Campus, France 6University of Massachusetts, Lowell, Massachusetts, USA 7Lawrence Berkeley Laboratory, Berkeley, California, USA 8Australian National University, Canberra, Australia 9Lawrence Livermore National Laboratory, Livermore, California, USA 10University of Maryland, College Park, Maryland
Interational Symposium on Super Heavy Nuclei 2015, Texas A&M
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Known isomers around Z=100 and N=152
Db
Sg
Rf
No
Md
Fm
Lr
254 252
256 3 iso???
254 257
255
255
250
257
261
253 250 iso sf hind?
253
3 short-‐lived isomers in 256Rf
isomer fission hindered in 250No
“blue” isotopes were studied at ATLAS
Dubna GSI Jyvaskyla LBNL GSI, Z=100
N=152
Interational Symposium on Super Heavy Nuclei 2015, Texas A&M 14
Trigger and Time control module
100MHz, 14-bit Digitizer M. Cromaz et al., A 597 (2008) 233–237
J.T. Anderson et al., 2007, IEEE Nuclear Science Symposium Conference Record, p. 1751
FMA Digital DAQ (based on GRETINA DAQ)
§ Trigerless § DSSD (320 chans) § X-‐array (20 chans) § focal plane (20 chans) § Resolu=on comparable
to analog (Ge/Si) § Pulse shape analysis § 100 kHz/DSSD possible § NEW FIRMWARE
PU pulses – fast decays
254Rf FMA results
Interational Symposium on Super Heavy Nuclei 2015, Texas A&M 15
§ 28 mass selected 254Rf fission events § 4 fast electron events (<10 µs) followed by 254Rf fission events § 1 slow electron (~500 µs) followed by 254Rf fission events
50Ti(206Pb,2n)254Rf, 2.4 nb, ~5 days, ~150 pnA
BGS experiment
Implant-decay spatial and time correlations in the DSSD
Q
e
Berkeley Gas-filled Separator
Beam
PPAC
Three 32X32 DSSD in box geometry
E,t
sf
50Ti(206Pb,2n)254Rf reaction 2.4 nb, ~5days , ~250 pnA
γ
3 clover HPGe α sf
2qp
4qp
e γgs
e γ
γ rays and conversion electrons deexciting isomers followed by α and sf decay
FGD
D
C3 setup
Charge state focusing results in ~x5-10 larger efficiency!
Interational Symposium on Super Heavy Nuclei 2015, Texas A&M 16
Interational Symposium on Super Heavy Nuclei 2015, Texas A&M 17
C3 detector three 32X32 DSSD log PAs
3 HPGe clover detectors large geometrical efficiency
Berkeley Gas-filled separator
254Rf level scheme
Interational Symposium on Super Heavy Nuclei 2015, Texas A&M 18
254Rf
4.7(1.1) µs mostly IT
23.2(1.1) µs mostly SF
2qp
gs
§ compared to lighter N=150 isotones 2qp isomer decay is x104 faster
§ no fission observed from the isomers: fission partial lifetimes are at least 2 and 25 longer for 2qp and 4qp isomers, respectively, relative to the gs
§ only 2nd 4qp isomer in the region
20%
247(73) µs mostly IT
4qp 2%
T1/2=23.2(1.1) µs
gs sf
T1/2=4.7(1.1) µs
T1/2=247(73) µs
el-el
im-el-sf 2qp+4qp
2qp el
2qp γ
4qp el
HSF>2
HSF>25
Ahmad et al., PRC 78, 034308 (2008)
Robinson et al., PRC 78, 034308 (2008)
Yates et al., PRC 12, 442 (1975)
Greenlees et al., PRC 78, 021303 (2008)
1.8 s
1.1 s
Interational Symposium on Super Heavy Nuclei 2015, Texas A&M 19
2qp isomer decays 10000 =mes faster than the isomers in the N=150 isotones!
Multi quasi-particle configuration calculations
Interational Symposium on Super Heavy Nuclei 2015, Texas A&M 20
Single-particle energies adjusted to experiment
Pairing: Lipkin-Nogami prescription. Blocking of 2 orbits. Pairing strengths: Gp=24/A, Gn=17.8/A Residual spin dependent interaction between unpaired nucleons
§ K=8-‐, 7/2+[624]9/2-‐[734] 2-‐quasineutron configura=on as in lighter N=150 isotones § K=8-‐, 7/2-‐[514]9/2+[624] 2-‐quasiproton state close in energy § 4-‐qp isomer is the K=16+ state resul=ng from coupling of the above excita=ons
254Rf level scheme
Interational Symposium on Super Heavy Nuclei 2015, Texas A&M 21
BUT how to explain the 2qp-‐isomer life=me which is 4 orders of magnitude shorter comared to the lighter N=150 isotones? § K=5-‐, ½-‐[521]9/2+[624] as proposed in 256Rf not supported by calcula=ons § accidental mixing with 8-‐ member of the octupole band
2qp el
2qp γ
4qp el
γ-‐ray spectrum similar to 252No and 250Fm
electron spectrum ~100 keV higher cut off
§ 2qp isomer ~100 keV higher § octupole band at the same energy § mixing with the 8-‐ octupole state
K-isomer fission hindrance
K-‐isomers cons=tute an interes=ng but challenging ground for tes=ng fission models
– role of K number (specializa=on energy) – Sta=c vs dynamic pairing (Yu. A. Lazarev, Phys. Scr. 1987) – Interplay of pairing and collec=ve degrees of freedom
J. Sadukham et al., PR C90, 061304 (R) (2014)
Interational Symposium on Super Heavy Nuclei 2015, Texas A&M 22
8-
16+
254Rf
F.G. Kondev, G.D. Dracoulis, T. Kibedi, accepted to ADNDT
One-‐dimensional approach with WKB approxima=on
AGFA - Argonne Gas-filled Fragment Analyzer
Intera=onal Symposium on Super Heavy Nuclei 2015, Texas A&M
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Enough space to accommodate a 4π Ge array Compact focal plane
B.B. Back, R.V.F. Janssens, W.F. Henning, T.L. Khoo, J.A. Nolen, D.H. Potterveld, G. Savard, D. Seweryniak, Argonne National Laboratory, M. Paul, Hebrew University, Jerusalem, Israel, P. Chowdhury, C.J. Lister, University of Massachusetts Lowell, W.B. Walters, University of Maryland, P.J. Woods, University of Edinburgh, K. Gregorich, Lawrence Berkeley National Laboratory, W. Loveland, Oregon State University
Combined function bending magnet+quadrupole
Summary
§ HK distribu=on was used to extract fission barrier in 254No § Two-‐ and four-‐quasipar=cle K-‐isomers were observed in 254Rf
– 2qp isomer decays 104 faster than 2qp isomers in the lighter N=150 isotones
– Second case of a 4qp isomer in the region was found – fission from the 2qp and 4qp isomers is hindered by a factor of at least 2 and 25 rela=ve to the ground state, respec=vely
– More beam will allow collec=ng 10x more sta=s=cs
§ We will con=nue these studies with AGFA and digital Gammsphere for heavier and more fissile heavy nuclei
Interational Symposium on Super Heavy Nuclei 2015, Texas A&M 24
Thank for your attention