1. GSI Experiments on Synthesis and Nuclear Structure Investigations of Heaviest Nuclei
F. P. Heßberger
Gesellschaft für Schwerionenforschung mbH, D Darmstadt, Germany
XII Nuclear Physics Workshop
Maria and Pierre Curie
Nuclear Structure Physics and Low Energy Reactions
September 2005, Kazimierz Dolny, Poland

2. Experimental Set-up at GSI GSI Experiments on Search for SHE
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

3. Predictions of Superheavy Elements
126
126
114
114 82 82
184
184
(164)
(164)
126
126
H. Meldner Arkiv fys. 36,593 (1967)

4. 114 82 d5/2 j15/2 9/2-[734] g9/2 100 96 f5/2 7/2+[624] f7/2 i13/2 h9/2
184
f5/2
7/2-[514]
d5/2
7/2+[624]
114
114
j15/2
152
f7/2
1/2-[521]
9/2-[734]
g9/2
i13/2
100
142
h9/2
3/2-[521] 96
134
126
7/2+[633]
1/2+[631] 82
Nilsson – Diagrams for Neutron (left) and proton (right) single particle levels

5. Production Mechanisms
Excerpt from Chart of Nuclei
Study of
Production Mechanisms
Search for SHE
Nuclear Structure
Investigations

6. Velocity separator SHIP
Separation time: – 2 μs
Transmission: – 50 %
Background: – 50 Hz
Det. E. resolution: – 25 keV
Det. Pos. resolution: μm
Dead time: μs
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7. Synthesis of SHE

8. confirmed - - disproved
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
σ/pb
Vassilissa 33
0.35
2 (ER-sf) 81
5.0
(Oganessian et al.) 39
0.22
<7.3
0.59
<2.2
35.5
0.47
568
3.0
DGFRS
31.4
0.58
1 (ER-[α]-sf)
3.4
/-0.4 (3n)
35.0
0.71
2 (ER-[α]-sf
3 (ER- α-sf)
1 (ER- 4α-sf)
1.4
2.7
6.1
/-1.1 (3n)
39.8
0.52
1 (ER-sf)
0.14 (ms)
/-0.6 (4n)
Chemistry (Yakushev et al.)
34.2
0.28
7 sf
>60 ≈2
BGS (Loveland,
31.9
0.226 -
<0.8
Gregorich et al.)
36.9
0.185
<0.96
SHIP
32.0
0.7
(Hofmann et al.)
34.5
1.0
5.2
/-0.6
37.0
1.2
<0.6
failed to confirm
confirmed disproved

9. 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 ≈ nb, i(48Ca) ≈ 1pμA  zα ≈ /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

10. Nuclear Structure Investigation of odd-A odd-Z nuclei

12. Comparison of theoretical and experimental Nilsson levels of odd mass Es - isotopes
a) Calculations of Cwiok et al. (black) and Parkhomenko and Sobiczewski (red)
b) experimental values
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

13. Deformation of odd-mass Es-isotopes as function of mass number Evidently: Relation between energy of 7/2- [514] level and deformation

14. Nuclear Structure Investigation of odd-A even-Z nuclei Example: Alpha-gamma decay measurements of 251No and its daughter products

15. Alpha – gamma – gamma coincidence measurements of 247Fm
 coincidences between K-x-rays  two transitions E > 136 keV
 coincidences of K-x-rays with keV and keV
 keV coincident with x-rays, keV but not with keV, which has a higher intensity than the keV line

16. Attempt to assign ‚gamma‘ – pairs to transitions:

17. (energies of gamma lines may differ slightly from
values on preceding foils)

18. Nilsson-Level systematics of N=151 isotones (even Z)

19. Nilsson - Level systematics of N=149 Isotones (even Z)

20. Nilsson-Level systematics of N = 147 Isotones (even Z)

21. Identifikation of a K-Isomer in 254No (R. Herzberg et al. , Exp
Identifikation of a K-Isomer in 254No (R.Herzberg et al., Exp. at RITU, Jyväskylä)
184 μs
266 ms
Spectra from confirmation experiment at SHIP 06/05

22. Identification of an isomeric state in 252No
gamma energies in keV

23. Conclusions ☺ Experimental results presently available
☺ ‘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 num-
ber;for element 113 only 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)

24. 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