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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


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


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


Determination of fission barrier from HK distribution


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

11

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


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

13

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


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


§  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!



C3 detector three 32X32 DSSD log PAs

3 HPGe clover detectors large geometrical efficiency

Berkeley Gas-filled separator

254Rf level scheme


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


2qp isomer decays 10000 =mes faster than the isomers in the N=150 isotones!

Multi quasi-particle configuration calculations


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


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)


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

23

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


Thank for your attention

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