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Spectroscopy of exotic nuclei
Lecture 4
Superheavy Elements (continued)
Shape coexistence
R. Krücken - XVth UK Postgraduate School in Nuclear Physics – Lecture 4
„Cold“ Fusion
• medium heavy projectile on doubly magic target 208Pb• low excitation energy of Compund nucleus• Evaporation of single neutron
Low excitation energy results from shell closure of target nucleus
„Cold“ Fusion
2R. Krücken - XVth UK Postgraduate School in Nuclear Physics –
Lecture 4
SHIP Experiment at GSI Darmstadt
Electric dipole
Magnetic dipoleBeam stop
Magneticquadrupole
Targetwheel
Position sensitivefocal plane
detector
Time of flightdetectorsMaximal: 0.3 particle mA = 2.1012 pps
3R. Krücken - XVth UK Postgraduate School in Nuclear Physics –
Lecture 4
eq
mvEρ
eq
mvBρ
2
Decay of 265Hs (Z=108)
Rf253
sf48 s
Rf254
sf
Rf256
sf,a
Rf257
a ,ec
4.7s
a,ec
Rf258
sf13 ms
Rf259
a,sf3.1 s
Rf260
sf21 ms
Rf261
a
78 sRf262
sf
47ms1.4sRf255
a,sf0.8s
a,sf1.4s 2.1s
sf
Db257
a,sf1.3 s
Db258
a,ec4.4 s
Db260
a,ec/sf?1.5 s
Db261
a,sf1.8 s
Db262
a ,ec/sf?34 s
Db263
a,sf27 s
Sg265
a,sf?7.4 s
Sg266
a,sf?21 s1.4s
Sg263
a0.3s
a ,sf?0.9s
Sg261
a ,ec0.23 s
Sg260
a ,sf3.6 ms
Sg259
a0.48 s
Sg258
sf2.9 ms
Bh261
a11.8 ms
Bh264
a440 ms
Bh262
a102ms
a8ms
Db256
a,sf2.6 s
Db255
a ,sf1.6 s
Bh260
a?
Hs263
a?
Hs264
a,sf0.45 ms
Hs265
a
0.8ms
a
1.7ms
a
Hs267
59 ms
Hs269
a 9.3 s
RfRuther-fordium
DbDubnium
SgSeaborgium
BhBohrium
HsHassium
105
106
107
108
150 152 154 156 158
160
N
a-decay Spont.anneous fission EC-decay
Z
Bh266
a» 1s
Bh267
a» 17 s
Hs266
2.3 msa a
Sg262
sf6.9 ms
23 s 6.1 s
• Successive decay must happen at same position
• a-energies must coincide with known decay energies
a-Energies
4R. Krücken - XVth UK Postgraduate School in Nuclear Physics –
Lecture 4
Gas-filled separator
• Magnetic field region filled with ~ 1 Torr He Gas
• Heavy ion leaves target with charge distribution
• Scattering of ion with gas (velocity of bound electrons)
charge exchange reactions narrow charge distribution around average charge state
Þ higher acceptance compared to vacuum system since only few charge states are accepted in vacuum system
• in first order magnetic rigidity B is independent of velocity since average charge state depends on velocity
large acceptance
BUT - Low mass resolution- Low background reduction
B = 0.0227 A v/v0 q-
1
q = v/v0 Z1/3
5R. Krücken - XVth UK Postgraduate School in Nuclear Physics –
Lecture 4
Dubna gas-filled separator
6R. Krücken - XVth UK Postgraduate School in Nuclear Physics –
Lecture 4
Hot Fusion
• light projectile onto actinide target è neutron rich isotope• high excitation energy of compound nucleus
Evaporation of several neutrons
Probability for „survival“ of compound nucleus: each evaporation of a neutron is in competition with fission
FN
NNP
xi
iNXN PP
...1
)(
Hot Fusion
7R. Krücken - XVth UK Postgraduate School in Nuclear Physics –
Lecture 4
Nuclear chart of transactinides in 2008
Rf253
sf48 s
Rf254
sf
Rf256
sf,a
Rf257
a,ec4.7sa,ec
Rf258
sf13 ms
Rf259
a,sf3.1 s
Rf260
sf21 ms
Rf261
a78 s
Rf262
sf47ms1.4s
Rf255
a,sf0.8s
a,sf1.4s 2.1s
sf
Db257
a,sf1.3 s
Db258
a,ec4.4 s
Db260
a,ec/sf?1.5 s
Db261
a,sf1.8 s
Db262
a,ec/sf?34 s
Db263
a,sf27 s
Sg265
a,sf?7.4 s
Sg266
a,sf?21 s1.4s
Sg263
a0.3s
a ,sf?0.9s
Sg261
a,ec0.23 s
Sg260
a,sf3.6 ms
Sg259
a0.48 s
Sg258
sf2.9 ms
Bh261
a11.8 ms
Bh264
a440 ms
Bh262
a102ms
a8ms
Db256
a,sf2.6 s
Db255
a,sf1.6 s
Bh260
a?
Hs263
a?
Hs264
a,sf0.45 ms
Hs265
a0.8ms
a1.7ms
a
Hs26759 ms
Hs269
a 9.3 s
Mt266
a1.7 ms
Mt268
a70 ms
110267
a?
110271
a1.1ms
a56 ms
110273
a76 ms
a118ms
269
a170 ms
110
272
a1.5 ms
111
112277
a194ms
a277ms
RfRuther-fordium
DbDubnium
SgSeaborgium
BhBohrium
HsHassium
MtMeitnerium
112
105
106
107
110
109
108
112
111
150 152 154 156 158
160
162
164
NA-decay Spont. fission EC-decay
Hs277
sf»10 min
281
a»1 min
285
a»10 min
112
110
289
a»20 s
114287
a»5 s
114
283
sf 3 min
112
114114
116
166 168
170 172
Z
116
174
284
a»10 s
112
a»2 s
114288
280
sf »7 s
110
Bh266
a» 1s
Bh267
a» 17 s
292
a» 33 ms
116
Hs2662.3 msa a
Sg262
sf6.9 ms
110270
a0.1ms
a6 ms
23 s 6.1 s
Darmstadtium (Ds)
“Problems” of Dubna results:
- decays often end in unknown isotopes
- short decay chains
- long correlation times283113 284113282113
286114
288115287115
290116 291116 293116
New elements/isotopes since 2001
294118118
115
113 176
Roentgenium (Rg)282112
278113
274Rg 278Rg 279Rg 280Rg
270Mt 276Mt275Mt274Mt
270Hs 271Hs275Hs
270Bh 271Bh 272Bh
267Sg 271Sg
266Db 268Db267Db259Db
263Rf 267Rf
hotfusion
279Ds
8R. Krücken - XVth UK Postgraduate School in Nuclear Physics –
Lecture 4
Copernicium (Cp)Suggestion:
Cross-sections
R. Krücken - XVth UK Postgraduate School in Nuclear Physics – Lecture 4
9
D. Ackermann
48Ca + 238U → 286112* - Summary
R. Krücken - XVth UK Postgraduate School in Nuclear Physics – Lecture 4
10
D. Ackermann
Independent confirmation of Dubna result !!
Spectroscopy of 254No
48Ca + 208Pb
Cross section: ~500 nb
(large due to doubly magic projectile and target nuclei)
11R. Krücken - XVth UK Postgraduate School in Nuclear Physics –
Lecture 4
Gamma spectroscopy of 254No at RITU
12R. Krücken - XVth UK Postgraduate School in Nuclear Physics –
Lecture 4
JUROGAM
Identification of 254No through a-decay
26 MeV 40 MeV
15 MeV 55 MeV
Implantation
Alpha decay
13R. Krücken - XVth UK Postgraduate School in Nuclear Physics –
Lecture 4
Rotational spectra in 254No
Gamma rays of nuclei at target position!!!
In coincidence with detected recoils
In coincidence with alpha decay transitions of 254No decay chain
14R. Krücken - XVth UK Postgraduate School in Nuclear Physics –
Lecture 4
SACRED
15R. Krücken - XVth UK Postgraduate School in Nuclear Physics –
Lecture 4
Conversion electrons guided by Solenoid magnet to segmented Si Detector
Confirmation of deformation of 254No
16R. Krücken - XVth UK Postgraduate School in Nuclear Physics –
Lecture 4
Chemistry of SHE
Situation as of one century ago
17R. Krücken - XVth UK Postgraduate School in Nuclear Physics –
Lecture 4
Periodic Table of the Elements
A. Türler, RCM, TUM
Does Hs behave like
Os?
18R. Krücken - XVth UK Postgraduate School in Nuclear Physics –
Lecture 4
Recoilchamber
269,270Hs
26Mg-beam
248Cm target
He/O2He/O2
2x 36PIN-diodes
PFA-tefloncapillary
thermostat
(-20°C)
N2(liq.) cooling
oven (600°C)
SiO2-column(i.D. 4 mm)
-170 °C
-20 °C
0 40 cm
HsO4 deposition
rotatingVacuum window
In-Situ Volatilization and On-line detection (IVO)
19R. Krücken - XVth UK Postgraduate School in Nuclear Physics –
Lecture 4
Shape coexistence
R. Krücken - XVth UK Postgraduate School in Nuclear Physics – Lecture 4
21
Predictions of superheavy nuclei
withshell corrections
withoutshell correction
Strutinsky, Nuclear Physics A951967
2nd minium at large deformation(superdeformation / shape coexistence)
22R. Krücken - XVth UK Postgraduate School in Nuclear Physics –
Lecture 4
Existence of superheavy nuclei
Shape coexistence in 152Dy
SD states become yrast at I » 60ħ
ProlateND Minimum
SD Minimum
OblateND Minimum
23R. Krücken - XVth UK Postgraduate School in Nuclear Physics –
Lecture 4
High spin spectroscopy
Population of nuclei at high angular momentumin Fusion-Evaporation-Reaction EUROBALL
24R. Krücken - XVth UK Postgraduate School in Nuclear Physics –
Lecture 4
Shape coexistence in 152Dy
linking transitions unknown
.)()2( constIEIEE
25R. Krücken - XVth UK Postgraduate School in Nuclear Physics –
Lecture 4
Superdeformation
SuperdeformationNuclei with long to shortAxis ratio of » 2:1
Around 250superdeformed bandshave been observed
Low-spin superdeformed states are at high energies with respect to ground state
26R. Krücken - XVth UK Postgraduate School in Nuclear Physics –
Lecture 4
Shape isomerism around 74Kr
R. Krücken - XVth UK Postgraduate School in Nuclear Physics – Lecture 4
27
M. Bender et al., PRC 74, 024312 (2006) Adopted from A. Görgen
Electron conversion spectroscopy
R. Krücken - XVth UK Postgraduate School in Nuclear Physics – Lecture 4
28
Isotope shifts in Hg
weaklyoblate deformed
stronglyprolate deformed
b = -0.1
b = -0.17
b = 0.25-0.28
...
10/,2,
6,,,,
AA
ElektronenAA
Feld
AAIS
AAFeld
AAMasse
AAIS
rF
Isotope shift (IS) of atomic transitions
Mean square charge radius <r2>
collinear laser spekctroscopy
29R. Krücken - XVth UK Postgraduate School in Nuclear Physics –
Lecture 4
Shape coexistence in 186Pb
Protonen-Konfigurationen
0p-0h 4p-4h2p-2hA. Andreyev et al., Nature 405, 430 (2000)
30R. Krücken - XVth UK Postgraduate School in Nuclear Physics –
Lecture 4
M(186Pb) ~ 174 GeV/c2
Subtle balance of nuclear forces leads to competition on the 1 MeV level (6∙10-6)
SHIP velocity filter at GSI
31R. Krücken - XVth UK Postgraduate School in Nuclear Physics –
Lecture 4
Shape coexistence in 186Pb – a-Spectra
“Penetration”-factor P depends on shape!
PT
Ih
100
)2ln(
2/1
2 Reduced a-width d2:Measure for creation ofa-particle in the nucleus Û p-h configuration
prolateoblate
spherical
Large overlap: (only protons)|Po;2p-0h> ® |Pb;0p-0h>|Po;4p-2h> ® |Pb;2p-2h>
analogy: spectroscopic factors
PoAPb
32R. Krücken - XVth UK Postgraduate School in Nuclear Physics –
Lecture 4
A. Andreyev et al., Nature 405, 430 (2000)
Shape coexistence in the light Hg nuclei
33R. Krücken - XVth UK Postgraduate School in Nuclear Physics –
Lecture 4
Plunger + Ritu@Jyväskylä
He at 1-2 mbar
C- foil
QDQ
Q
target
RITU separator~ 30% recoil eff. beam
JUROGAM Ge-array~ 4% efficiency
34R. Krücken - XVth UK Postgraduate School in Nuclear Physics –
Lecture 4
T. Grahn et al., PR L97 (2006) 062501 T. Grahn et al., PRC80 (2009) 014324
Lifetime measurement in 180Hg
R. Krücken - XVth UK Postgraduate School in Nuclear Physics – Lecture 4
35
T. Grahn et al., PRC 80, 014324 (2009)
Coulex of 184,186,188Hg at REX-ISOLDE
184Hg
Online spectrumTarget: 120Sn
P. Butler et al.
535 keV22
+ 01+
287 keV41
+ 21+
367 keV21
+ 01+
01+
21+
22+
41+
02+
Aim:- Measure E2 transition and diagonal matrix elements deformations
36R. Krücken - XVth UK Postgraduate School in Nuclear Physics –
Lecture 4
Superheavy elementsNuclear Structure at the extremes
New shell gaps through residual interaction
Shell quenching bydiffuse surface
Halos
Soft collective modes
Neutron Skins
Shape coexistence
Cluster
Isospin competitionand symmetry
37R. Krücken - XVth UK Postgraduate School in Nuclear Physics –
Lecture 4
Thank you for your attention!!
R. Krücken - XVth UK Postgraduate School in Nuclear Physics – Lecture 4
38