GSI Experiments on Synthesis and
Nuclear Structure Investigations of
Heaviest Nuclei
F. P. Heßberger
Gesellschaft für Schwerionenforschung mbH,
D-64291 Darmstadt, Germany
XII Nuclear Physics Workshop
Maria and Pierre Curie
Nuclear Structure Physics and Low Energy Reactions
21.-25. September 2005, Kazimierz Dolny, Poland
Outline of the talk




Physical Motivation
Experimental Set-up at GSI
GSI Experiments on Search for SHE
GSI Experiments on Nuclear Structure
Investigations of Transfermium Isotopes
-- Decay Studies of odd-mass odd-Z nuclei
-- Decay Studies of odd-mass even-Z nuclei
-- Systematic Trends in Single Particle Levels
-- K-Isomers in even-even nuclei
• Conclusions
• Collaborations
126
114
126
114
82
Proton number
Predictions of Superheavy Elements
82
120
118
116
114
112
110
108
106
104
102
100
Sobiczewski
& Smolanczuk
-2
-3
-7
-4
-5
-6
-6
-7
-3
-4
-5
-4
-3
140 145 150 155 160 165 170 175 180 185 190
184
184
(164)
(164)
126
126
Proton number
Neutron number
120
118
116
114
112
110
108
106
104
102
100
Möller et al.
-8
-7
-9
-6
-4
-6
-7
-5
-1 -2-3
-4
-3
140
150
160
-2
-1
-2
170
-3
180
190
Neutron number
H. Meldner Arkiv fys. 36,593 (1967)
F.P.Heßberger /konferenzen/Kazimiersz/ 12.9.2005
184
d5/2
7/2+[624]
114
114
152
j15/2
9/2-[734]
g9/
h9/2
134
1/2-[521]
f7/2
i13/2
142
2
7/2-[514]
f5/2
100
96
3/2-[521]
7/2+[633]
126
1/2+[631]
82
Nilsson – Diagrams for Neutron (left) and proton (right) single particle levels
Excerpt from Chart of Nuclei
Velocity separator SHIP
SHIP
Separation time:
1 – 2 μs
Transmission:
20 – 50 %
Background:
10 – 50 Hz
Det. E. resolution:
18 – 25 keV
Det. Pos. resolution: 150 μm
Dead time:
25 μs
Mastertitelformat bearbeiten
Synthesis of SHE
10000
'cold' fusion (Pb,Bi-targets)
34
S + actinide targets
48
1000
Ca + actinide targets (3n)
48
Ca + actinide targets (4n)
 / pbarn
100
10
1
0,1
104 106 108 110 112 114 116 118
ZER
konferenzen/kazimiersz/quersschn 13.9.2005
Basic Rule in Physics:
Experimental results have to be reproduced independently before being generally accepted
Reaction 238U(48Ca,xn) 276-x112 are technically ‚easy‘ to perform  a ‚key‘ to SHE
E* / MeV Dose/10-19
events
T1/2 /s
81
σ/pb
Vassilissa
33
0.35
2 (ER-sf)
5.0
(Oganessian et al.)
39
0.22
0
<7.3
33
0.59
0
<2.2
35.5
31.4
35.0
0.47
0.58
0.71
568
3.4
1.4
2.7
6.1
0.14 (ms)
>60
3.0
0.5 +1.2/-0.4 (3n)
Chemistry
39.8
34.2
0.52
0.28
2 (ER-sf)
1 (ER-[α]-sf)
2 (ER-[α]-sf
3 (ER- α-sf)
1 (ER- 4α-sf)
1 (ER-sf)
7 sf
(Yakushev et al.)
BGS (Loveland,
Gregorich et al.)
31.9
36.9
0.226
0.185
0
0
-
<0.8
<0.96
SHIP
32.0
0.7
0
-
<0.8
(Hofmann et al.)
34.5
1.0
1 (ER-sf)
5.2
0.7 +1.6/-0.6
37.0
1.2
0
-
<0.6
DGFRS
(Oganessian et al.)
2.5 +1.8/-1.1 (3n)
0.6 +1.6/-0.6 (4n)
≈2
Nuclear Structure Investigations of Transfermium Isotopes
What can be (presently) achieved by decay studies ?
Production rates:
 207Pb(48Ca,2n)253No : σ ≈ 900 nb, i(48Ca) ≈ 1pμA  z α ≈ 7000 /h
 206Pb(48Ca,3n)251No : σ ≈ 25 nb, i(48Ca) ≈ 1pμA  zα ≈ 200 /h
 207Pb(50Ti,2n)255Rf : σ ≈ 10 nb (50% sf), i(50Ti) ≈ 0.4pμA  zα ≈ 20/h
 209Bi(40Ar,2n)247Md : σ ≈ 7 nb, i(40Ar) ≈ 1.5pμA  zα ≈ 40 /h
 Collection of several (ten) thousand decays within several days
 Fine structure measurements possible, but not sufficient for detailed level
schemes (like for nuclei where weighable amounts are available)
 Establishing global trends in nuclear structure (for some Nilsson levels)
 Similarities in Nuclear Structure along the ‚Isotope Line‘ in odd-Z nuclei
 Similarities in Nuclear Structure along the ‚Isotone Line‘ in even-Z nuclei
Nuclear Structure Investigation of odd-A odd-Z nuclei
- - correlations observed for
50
Ti +
209
Bi -->
259
Spectrum of -events in prompt
251
coincidence with -decays of Md
Db* at E = 4.85 AMeV
250
257m
Db
9000
Lr
Lr
8800
253m
Lr
Lr
258
( Db
254
--> Lr)
8400
4
150
300
100
242.7
E (daughter) / keV
253g
events
253m
8600
8
200
counts
253g
8200
249
8000
Md
354.8
376.9
Db
303.2
257g
293.7
9200
350
400
E / keV
50
7800
0
100
7600
8700 8800 8900 9000 9100 9200 9300 9400
E (mother) / keV
F.P.Heßberger 12.9.2005
150
200
250
300
E / keV
350
400
450
F.P.Heßberger 12.9.2005
209
50
209
257
Bi( Ti,2n) Db
Present status of nuclear structure
investigations of odd A odd Z elements
in the region Z=99-105
48
255
Bi( Ca,2n) Lr
207
-
Level assignments are partly tentive
257
9074
8967
253
+
9/2 [624] ?
+
9/2 [624]
9163
48
Pb( Ca,2n) No -EC->
1/2 [521]
259
Db
9474
Md
+
9/2 [624] ?
261
Db
253
8930
Db
-
1/2 [521]
-
1/2 [521]
-
9/2 ?
7/2 [514]
no 
209
40
8722
247
Bi( Ar,2n) Md
253
8794
-
7/2 [514]
8470
(8385)
Lr
-
247
8861
249
259
Lr
Lr
8450
-
9/2 ?
7/2 [514]
-
7/2 [514]
Md
8796
1/2 [521]
-
-
sf
257
Lr
?
7/2 [514]
-
7/2 [514]
-
1/2 [521]
no 
-
1/2 [521]
255
8385
(8470)
-
7/2 [514]
7/2 [514]
251
Md
253
Md
Md
-
7/2 [514]
255
7327
7274
Md
-
8030
8421
7540
9/2
7/2 [514]
7100
8785
7714
-
7/2 [514]
405
(E1)
-
7/2 [514]
-
1/2 [521]
-
7/2 [514]
-
7/2 [514]
157 210
(E1)
243
Es
200
253
(E1)
294
(E1)
245
Es
353
(E1 ?)
7752
453
(E1)
+
9/2
+
7/2 [633]
3/2 [521] ?
9/2
+
9/2 (?)
+
+
9/2
+
7/2 [633]
3/2 [521] ?
243
247
-
Es
3/2 [521] ?
+
+
+
7/2 [633]
7/2 [633]
7/2 [633]
-
249
Es
3/2 [521] ?
251
-
Es
3/2 [521]
FPH 12.9.2005
Comparison of theoretical and experimental Nilsson levels of odd mass Es
- isotopes
900
a)
800
-
700
*
E / keV
a) Calculations of Cwiok et al.
(black) and Parkhomenko and
Sobiczewski (red)
b) experimental values
7/2 [514]
600 7/2 [514]
500
-
1/2 [521]
400 1/2 [521]
300 3/2 [521]
-
3/2 [521]
200 3/2-[521]
-
1/2 [521]
100
+
7/2 [633]
0
Es-243 Es-245 Es-247 Es-249 Es-251 Es-253 Es-255
b)
-
400
352+x
7/2 [514]
295+x
300
*
E / keV
500
253+x
210+x
200
-
3/2 [521]
100
0
0+x
0+x
0+x
0+x
+
7/2 [633]
Es-243 Es-245 Es-247 Es-249 Es-251 Es-253
 Trend of increasing energy
with increasing N satisfactoily
reproduced by Cwiok et al.
but maximum at Es-249
 Opposite trend predicted by
Parkhomenko and
Sobiczewski
 Ground state predicted as
7/2+[633]; situation not fully
clear from experimental side
 Energies of the 7/2-[514] –
levels differ by several
hundreds of keV
Deformation of odd-mass Es-isotopes as function of mass
number
Evidently: Relation between energy of 7/2- [514] level and deformation
500
0,252
0,248
450
Ref. PaS04
Ref. Cwi95
Ref. MoNi95
400
350
0,244
300
250
E / keV
2
0,240
0,236
0,232
200
E((7/2-[514])-(7/2+[633]))
70
60
0,228
50
0,224
40
0,220
238 240 242 244 246 248 250 252 254 256 258
Mass Number
E((9/2+)-(7/2+))
30
242
Fig. 5
1. 6. 2005
244
246
248
250
Mass Number
252
254
Nuclear Structure Investigation of odd-A even-Z nuclei
Example: Alpha-gamma decay measurements of 251No and its daughter products
200
166.6
105.5
152.1
250
82.2
Ereignisse
0
E / keV
141.8
100
500
K (Cf)
121.8
251m
No
Fm
247m
252
Cf
Cf
244
1000
247
Fm
1500
243
counts
2000
No
251
No
K (Cf)
2500
10
150
100
50
1
0
7000
7500
8000
E / keV
8500
9000
80
100
120
E / keV
140
160
F.P.Heßberger 28.4.2005
Alpha – gamma – gamma coincidence measurements of
247Fm
 coincidences
between K-x-rays  two transitions E > 136 keV
 coincidences of K-x-rays with 121.9 keV and 166.3 keV
 121.9 keV coincident with x-rays, 141.8 keV but not with 166.3 keV,
which has a higher intensity than the 141.8 keV line
12
 coinc. K - xrays
8
4
0
4
 coinc. 121.9 keV
counts
2
0
4
 coinc. 141.8 keV
2
0
4
 coinc. 166.3 keV
2
0
80
100
120
140
E / keV
160
180
200
Attempt to assign ‚gamma‘ – pairs to transitions:
Möller-Nix
60
(141.8-82.2)
56
55
52
50
48
45
(166.6-121.8)
44
40
60
Sobiczewski et al.
(141.8-82.2)
56
52
48
Möller-Nix
(141.8-82.2)
(166.6-121.8)
Th
U
Pu
Cm
40
35
60
Sobczewski et al.
(141.8-82.2)
55
50
45
(166.6-121.8)
(166.6-121.8)
44
Th
U
Pu
Cm
40
40
0,20
E(5/2+-->3/2+)1/2+[631] / keV
E(7/2+-->5/2+[622]) / keV
60
35
0,21
0,22
0,23
 (gs)
0,24
0,25
0,26
F.P.Heßberger 27.4.2005
0,20
0,21
0,22
0,23
0,24
0,25
0,26
2 (gs)
F.P.Heßberger 27.4.2005
251
Preliminary Decay schemes of
251
247
No and Fm
~90
247
Fm
gs
E = 8668 keV, HF = 2.0
5.1 s
~30
1.04 s
+
(1/2 [631])
0.85 s
+
(7/2 [624])
E = 8608 keV, HF = 1.1
+
(1/2 [631])
31 s
gs
No
+
(7/2 [624])
E ~7840 keV
HF ~0.8
(7/2 [624])
166.6
(M1+E2)
121.8
~10
gs
+
(5/2 )
+
(3/2 )
+
(1/2 [631])
Cf
239
Pu
209.7 (3.5)
82.2
228.2 (11.3)
(5/2 [622])
141.8
(M1+E2)
E = 8171 keV
HF = 1.3
5/2 [622]
277.6 (15.0)
+
+
+
285.5 (0.8)
(7/2 )
243
7/2
+
~196
~70
181.7 (1.1)
+
~318
~152
226.4 (3.3)
+
7/2 [624]
+
7/2
+
5/2
+
3/2
+
1/2 [631]
F.P.Heßberger 2.5.2005
Nilsson-Level systematics of N=151 isotones (even Z)
800
+
3/2 [622]
+
700
3/2 [622]
600
1/2 [620]
+
+
1/2 [620]
+
1/2 [631]
+
5/2 [622]
+
400
1/2 [620]
+
3/2 [622] ?
+
5/2 [622]
*
E / keV
500
300
+
7/2 [624]
+
5/2 [622]
200
+
7/2 [624]
25s
23s
+
23s
7/2 [624]
45s
100
-
-
0
9/2 [734]
247
Cm
249
Cf
251
Fm
Experiment
253
No
9/2 [734]
9/2 [734] 247
Cm
249
Cf
251
Fm
253
No
255
Rf
Calculation Cwiok et al. Nucl. Phys. A573 (1995)
Calculation Sobiczewski et al. Priv. Comm. 2005
Nilsson - Level systematics of N=149 Isotones (even Z)
-
1/2 [631]
500
500
-
400
9/2 [734]
400
+
E / keV
300
*
300
+
5/2 [622]
*
E / keV
1/2 [631]
200
200
+
5/2 [622]
100
100
-
9/2 [734]
+
0
-
7/2 [624]
243
Pu
245
Cm
247
Cf
experiment
249
Fm
251
No
0
7/2 [624]
243
Pu
245
Cm
247
Cf
249
Fm
251
No
253
Rf
255
Sg
Calculations Sobiczewski et al. priv. comm. 2005
Nilsson-Level systematics of N = 147 Isotones (even Z)
-
450
450
400
400
350
350
300
E / keV
7/2 [743]
250
*
200
+
1/2 [631]
300
-
*
E / keV
9/2 [734]
+
7/2 [624]
150
-
7/2 [743]
250
+
7/2 [624]
200
150
+
100
1/2 [631]
100
50
50
+
+
0
5/2 [622]
239
U
241
Pu
243
Cm
experiment
245
Cf
247
Fm
0
5/2 [622]
239
U
241
Pu
243
Cm
245
Cf
247
Fm 249No
251
Rf
253
Sg
calculations Sobiczewski et al., priv. comm 2005
F.P.Heßberger 5.9.2005
267
8+
214
6+
159
4+ 102
2+ 44
0+
887 942
corr. ER within 500 ms
200
100
0
corr. ER within 0.5 ms
100
200
844
887
943
10+
Fm-X-rays
53
318
events
20
includes
= decay
53 (E1)
and 606 keV 15
7+
8- CE184
82
6+
1293 keV μs
10
69
5+
266
57
4+
5
45 988 keV ms
3+
0
844
300
K=3
12+
K=8
2.5 MeV?
606
Identifikation of a K-Isomer in 254No
(R.Herzberg et al., Exp. at RITU, Jyväskylä)
600 700 800 900
E / keV
Spectra from confirmation experiment at SHIP 06/05
Identification of an isomeric state in 252No
counts
Corr. ER - e_ - ,sf t<10 s
20
10
0
0
40
80
at 1.4 MeV (Chu et al.) 90+-25 ms
12+
328
20
0
30
 7/2+[633] x 7/2-[514] ca. 1.3 MeV
920
862
885
911
828
755
238
208 (Np)
224 (8+-->6+)
40
Corr. ER - e_, t < 500 ms
167 (6+-->4+)
60
107 (4+-->2+?)
134
237
59.5 Np)
(
80
Pu -x-rays
Reaction: 48Ca + 206Pb, E = 4.6 AMeV
Spectrum -rays coinc. with electrons (E < 250 keV, t<500 ms)
10+
277
8+
224
6+
167
4+
2+ 107
0+ 46
7- ?
134 ?
ca. 1 MeV
755, 828, 862,
885, 911, 920
Sketch of the decay of 252mNo
120 160 200 240 720 760 800 840 880 920 960 1000
E / keV
F.P.Heßberger 20.9.2005
gamma energies in keV
Conclusions






☺ ‘Cold’ fusion reactions have been a successful method to produce isotopes of elements
up to Z = 113; however, cross sections decrease drastically with increasing atomic number;for element 113 only 0.055 pb were measured (but probably not the maximum)
☺ ‘Hot’ fusion reactions may be a suited method to produce SHE; interesting results have
been obtained from DGFRS, but could not be confirmed in other laboratories so far;
more effort is needed

☺ To better understand the properties of heaviest known nuclei and to get a firm base for
reliable predictions of nuclear properties in the expected region of (spherical)
superheavy nuclei detailed investigations of nuclear structure are indispensable;
experimental tools are α -γ- (α –CE)-decay spectroscopy or in-beam spectroscopy

☺ Experimental results presently available













 allow to follow systematics in the energy of single particle levels in N = 145, 147,
149 and 151 isotones with even atomic numbers up to Z = 102
 indicated close similarities in the nuclear structure of neutron deficient isotopes with
even neutron numbers of odd Z elements in the region einsteinium to dubnium
☺ Production rates indicate, that detailed nuclear structure
investigations by means of -
- coincidence measurements are possible with present techniques down to cross
sections of 100pb (265Hs)
 ‘On and on but the road is never ending, at least we know, we’re on our way’
(from ‘On and on’ by Fiddler’s Green)
Collaboration
GSI, Darmstadt
S. Hofmann, D. Ackermann,
B. Kindler, I.Kojouharov,
P. Kuusiniemi, B. Lommel,
R. Mann, K. Nishio,
B. Sulignano, F.P.H
University Bratislava, Slovakia
S. Antalic, S. Saro, B. Streicher,
M. Venhart,
P. Cagarda (until 2003)
University Jyväskylä, Finland
M. Leino, J. Uusitalo
FLNR-JINR Dubna, Russia
A.G. Popeko, A.N. Eremin
University Liverpool, UK
R.-D. Herzberg
University Warsaw, Poland
A. Sobiczewski, A. Parkhomenko