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Spectroscopy of exotic nuclei Lecture 4

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1 Spectroscopy of exotic nuclei Lecture 4
Superheavy Elements (continued) Shape coexistence R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

2 „Cold“ Fusion „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 R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

3 SHIP Experiment at GSI Darmstadt
Time of flight detectors Maximal: 0.3 particle mA = pps Position sensitive focal plane detector Beam stop Target wheel Magnetic dipole Electric dipole Magnetic quadrupole R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

4 Decay of 265Hs (Z=108) a-Energies
263 Hs 264 Hs 265 Hs 266 Hs 267 Hs 269 Hs Hassium ? 0.45 ms 0.8ms 1.7ms 2.3 ms a 59 ms  9.3 s a a ,sf a a a a a Bh 107 260 Bh 261 Bh 262 Bh 264 Bh 266 Bh 267 Bh ? 11.8 ms 102ms 8ms 440 ms » 1s » 17 s Bohrium a a a a a a a 106 Sg 258 Sg 259 Sg 260 Sg 261 Sg 262 Sg 263 Sg 265 Sg 266 Sg 2.9 ms 0.48 s 3.6 ms 0.23 s 6.9 ms 1.4s 7.4 s 21 s Seaborgium sf a a ,sf a ,ec 0.3s 0.9s sf a a ,sf? a ,sf? a ,sf? 105 Db 255 Db 256 Db 257 Db 258 Db 260 Db 261 Db 262 Db 263 Db 160 1.6 s 2.6 s 1.3 s 4.4 s 1.5 s 1.8 s 34 s 27 s Dubnium a ,sf a ,sf a ,sf a ,ec a ,ec/sf? a ,sf a ,ec/sf? a ,sf Rf 253 Rf 254 Rf 255 Rf 256 Rf 257 Rf 258 Rf 259 Rf 260 Rf 261 Rf 262 Rf fordium Ruther- 48 s 23 s 0.8s 1.4s 1.4s 6.1 s 4.7s 13 ms 3.1 s 21 ms 78 s 47ms 2.1s sf sf a ,sf a ,sf sf, a a ,ec a ,ec sf a ,sf sf a sf sf 150 152 154 156 158 N a-decay Spont.anneous fission EC-decay Successive decay must happen at same position a-energies must coincide with known decay energies R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

5 Gas-filled separator q = v/v0 Z1/3 B = 0.0227 A v/v0 q-1
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 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 = A v/v0 q-1 q = v/v0 Z1/3 R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

6 Dubna gas-filled separator
R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

7 Hot Fusion 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 R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

8 Nuclear chart of transactinides in 2008
“Problems” of Dubna results: decays often end in unknown isotopes short decay chains long correlation times 118 294118 116 290116 291116 116 292 116 293116 a » 33 ms 287115 288115 115 114 286114 114 287 114 288 114 289 114 a »5 s a »2 s a »20 s 113 278113 282113 283113 284113 Copernicium (Cp) 176 Suggestion: 112 112 277 112 282112 283 112 284 112 285 112 Roentgenium (Rg) 194ms 277ms  3 min »10 s »10 min a a sf a a 272 111 274Rg 278Rg 279Rg 280Rg 111 174 a 1.5 ms Darmstadtium (Ds) 267 110 269 110 270 110 271 110 110 273 110 279Ds 280 110 281 110 ? 170 m s 0.1ms 6 ms 1.1ms 56 ms a a a a a 76 ms 118ms sf »7 s a »1 min a a a 109 Mt 266 Mt 268 Mt 270Mt 274Mt 275Mt 276Mt 170 172 Meitnerium 1.7 ms 70 ms a a 108 Hs 263 Hs 264 Hs 265 Hs 266 Hs 267 Hs 269 Hs 270Hs 271Hs 275Hs 277 Hs Hassium a ? a 0.45 ms ,sf 0.8ms 1.7ms 2.3 ms 59 ms  9.3 s »10 min hot fusion a a a a a a sf 107 Bh 260 Bh 261 Bh 262 Bh 264 Bh 266 Bh 267 Bh 270Bh 271Bh 272Bh Z Bohrium ? 11.8 ms 102ms 8ms 440 ms » 1s 166 168 a a a a a a a » 17 s 106 Sg 258 Sg 259 Sg 260 Sg 261 Sg 262 Sg 263 Sg 265 Sg 266 Sg 267Sg 271Sg 2.9 ms 0.48 s 3.6 ms 0.23 s 6.9 ms 0.3s 1.4s 0.9s 7.4 s 21 s Seaborgium sf a a ,sf a ,ec sf a a ,sf? a ,sf? a ,sf? 105 Db 255 Db 256 Db 257 Db 258 Db 259Db 260 Db 261 Db 262 Db 263 Db 266Db 267Db 268Db Dubnium 1.6 s 2.6 s 1.3 s 4.4 s 1.5 s 1.8 s 34 s 27 s 160 164 a ,sf a ,sf a ,sf a ,ec a ,ec/sf? a ,sf a ,ec/sf? a ,sf Rf 253 Rf 254 Rf 255 Rf 256 Rf 257 Rf 258 Rf 259 Rf 260 Rf 261 Rf 262 Rf 263Rf 267Rf 1.4s 162 fordium Ruther- 48 s 23 s sf sf 0.8s a ,sf 1.4s 6.1 s a ,sf sf, a 4.7s 13 ms 3.1 s 21 ms 78 s 2.1s a ,ec a ,ec sf a ,sf sf a 47ms sf sf 150 152 154 156 158 N A-decay Spont. fission EC-decay New elements/isotopes since 2001 R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

9 Cross-sections D. Ackermann
R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

10 48Ca + 238U → * - Summary D. Ackermann Independent confirmation of Dubna result !! R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

11 Spectroscopy of 254No 48Ca + 208Pb Cross section: ~500 nb
(large due to doubly magic projectile and target nuclei) R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

12 Gamma spectroscopy of 254No at RITU
JUROGAM R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

13 Identification of 254No through a-decay
26 MeV 40 MeV Implantation 15 MeV 55 MeV Alpha decay R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

14 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 R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

15 SACRED Conversion electrons guided by Solenoid magnet to segmented Si Detector R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

16 Confirmation of deformation of 254No
R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

17 Situation as of one century ago
Chemistry of SHE Situation as of one century ago Periodic Table of the Elements R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

18 Does Hs behave like Os? A. Türler, RCM, TUM
R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4 A. Türler, RCM, TUM

19 In-Situ Volatilization and On-line detection (IVO)
26Mg-beam rotating Vacuum window 248Cm target 2x 36 PIN-diodes PFA-teflon capillary thermostat (-20°C) N2(liq.) cooling He/O2 Recoil chamber 269,270Hs oven (600°C) SiO2-column (i.D. 4 mm) -170 °C -20 °C 40 cm HsO4 deposition R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

20 PIN Diode detector system
R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

21 Shape coexistence R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

22 Predictions of superheavy nuclei
with shell corrections without shell correction Existence of superheavy nuclei 2nd minium at large deformation (superdeformation / shape coexistence) Strutinsky, Nuclear Physics A95 1967 R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

23 Shape coexistence in 152Dy
Oblate ND Minimum Prolate ND Minimum SD states become yrast at I » 60ħ SD Minimum R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

24 High spin spectroscopy
Population of nuclei at high angular momentum in Fusion-Evaporation-Reaction EUROBALL R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

25 Shape coexistence in 152Dy
linking transitions unknown R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

26 Superdeformation Superdeformation Nuclei with long to short Axis ratio of » 2:1 Around 250 superdeformed bands have been observed Low-spin superdeformed states are at high energies with respect to ground state R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

27 Shape isomerism around 74Kr
M. Bender et al., PRC 74, (2006) Adopted from A. Görgen R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

28 Electron conversion spectroscopy
R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

29 Isotope shifts in Hg Isotope shift (IS) of atomic transitions strongly
weakly oblate deformed strongly prolate b = -0.1 b = -0.17 b = Mean square charge radius <r2> collinear laser spekctroscopy R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

30 Shape coexistence in 186Pb
Protonen-Konfigurationen 4p-4h 2p-2h 0p-0h M(186Pb) ~ 174 GeV/c2 Subtle balance of nuclear forces leads to competition on the 1 MeV level (6∙10-6) A. Andreyev et al., Nature 405, 430 (2000) R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

31 SHIP velocity filter at GSI
R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

32 Shape coexistence in 186Pb – a-Spectra
A. Andreyev et al., Nature 405, 430 (2000) Reduced a-width d2: Measure for creation of a-particle in the nucleus Û p-h configuration prolate oblate spherical Large overlap: (only protons) |Po;2p-0h> ® |Pb;0p-0h> |Po;4p-2h> ® |Pb;2p-2h> analogy: spectroscopic factors “Penetration”-factor P depends on shape! R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

33 Shape coexistence in the light Hg nuclei
R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

34 Plunger + Ritu@Jyväskylä
JUROGAM Ge-array ~ 4% efficiency He at 1-2 mbar Q Q D Q RITU separator ~ 30% recoil eff. beam T. Grahn et al., PR L97 (2006) T. Grahn et al., PRC80 (2009) target C- foil R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

35 Lifetime measurement in 180Hg
T. Grahn et al., PRC 80, (2009) R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

36 Coulex of 184,186,188Hg at REX-ISOLDE
Online spectrum Target: 120Sn 367 keV 21+ 01+ 184Hg 41+ 22+ 21+ 02+ 287 keV 41+ 21+ 535 keV 22+ 01+ 01+ Aim: - Measure E2 transition and diagonal matrix elements  deformations R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4 P. Butler et al.

37 Nuclear Structure at the extremes Superheavy elements
Shape coexistence Isospin competition and symmetry Shell quenching by diffuse surface Cluster Neutron Skins New shell gaps through residual interaction Soft collective modes Halos R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

38 Thank you for your attention!!
R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

39 Alpha-Q-values in comparison to theory
R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

40 Predicted deformed shell at N=152
P. Moeller, J.R. Nix, W.D. Myers, W.J. Swiatecki, At. Data Nucl. Data Tables 59 (1995) 185 R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

41 Conversion electrons - example No
Only 11% of 6 → 4 intensity visible in g-spectrum, but only 1.5% of 4 → 2 transition  rest is emitted in conversion electrons In addition the gamma efficiency at 102 keV is lower compared to 160 keV  4 → 2 and 2→ 0 transitions are not visible in gamma-ray spectra!! R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

42 Conversion electron spectroscopy
R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

43 Decy curve 52 (5) s ~ 1000 s R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

44 From shell closure to mid shell
R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

45 Nuclear deformation Entwicklung der Kernoberfläche in Kugelfächenfunktionen Quadrupole Octupole Hexadecupole Laborsystem R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

46 Shape coexistence in 56Ni
Rotational bands in a Doubly magic nucleus!?! ç oblat Deformation prolat è Nilsson-Model: Single-particle orbitals in a Deformed oszillator potential Excitation costs little energy ... Nucleons in orbitals oustside closed shells Þ deformed nuclear shape R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

47 Velocity filter SHIP at GSI Darmstadt
R. Krücken XVth UK Postgraduate School in Nuclear Physics – Lecture 4

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