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Opportunities for Spectroscopy of super heavy elements

Opportunities for Spectroscopy of super heavy elements. Overview. In-beam Spectroscopy of SHE is a very successful technique Complementary to Decay Studies Optical Studies. Scientific Goals. Single Particle structure of SHE Detailled in-beam spectroscopy of nuclei

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Opportunities for Spectroscopy of super heavy elements

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  1. Opportunities for Spectroscopy of super heavy elements R-D Herzberg

  2. Overview • In-beam Spectroscopy of SHE is a very successful technique • Complementary to Decay Studies • Optical Studies

  3. Scientific Goals • Single Particle structure of SHE • Detailled in-beam spectroscopy of nuclei from Cf to Ds and beyond • Anchor “floating” chains • Ideally follow the stability line… • … or at least stay as close to it as possible.

  4. Why study transfermiums? Nobelium region is ideal for this: “Large” Cross sect. f5/2 - f7/2 probed Systematics possible Deformation brings strongly downsloping orbitals from above the next spherical shell gap close to the Fermi surface.

  5. Magic Shells M Bender et al, PLB

  6. Decay Studies • Important for ground state properties: • Mass (≠ Q-value) • Spin + Parity • Decay modes • Lifetime • Shape • Confirmation of chains • Unambiguous (Z,N) identification

  7. 3·109132Sn on various targets -7 MeV -6 MeV -5 MeV -4 MeV -3 MeV 120 Shell-Correction Energies 114 112 110 108 R. Smolanczuk et al., Phys. Rev. C 52, 1872(1995) R. Smolanczuk and A. Sobiczewski, Proc. XV Nucl. Phys. Div. Conf., Singapore (1995), p. 313 S. Hofmann, Nucl. Phys. News Intl

  8. In-beam Studies • Experience with gamma and CE studies • Unique set of problems • Main challenge is Fission

  9. gK ~ 0.7Mainly E2 E2 7+2 [633] 7-2 [514] 7+ 2 M1 7- 2 gK~1.3 MainlyM1 1-2 [521] Mainly E2 a ~ 0.9: 1- 2 251Md • B(M1)/B(E2)  K2(gK-gR)2/Q02 C. Theisen priv comm.

  10. 251Md First rotational band firmly established in an odd transfermium nucleus C. Theisen/A Chatillon priv comm.

  11. MoI 2 A. Afanasiev, PRC 67, 24309, (2002)

  12. Isomers • Provide information on quasiparticle states • Indirect evidence for isomer in 254Noseen in the 1970s A. Ghiorso et al, PRC 7 (1973) 2032 • Several searches in JYFL and ANL

  13. α e Isomer Tagging • Use the DSSD as a calorimeter! GD Jones, NIM A488, 471 (2002) Jurogam Array DSSD Pixel γ γ Isomer decay γ Target Chamber Followed by Alpha decay Prompt Gammas

  14. 2.6 184 ms (8-) 1.4 266 ms 0+ Experiment Interpretation

  15. Already Done Potentially Doable Feasibility depends On the specifics in Each and every case! Which Cases? ProtonNumber Neutron Number

  16. How to get there? • Available Targets: • 208Pb, 209Bi (Cold fusion) • 232Th, 238U, 243Am, 248Cm (Hot Fusion) • Beams: Far out.

  17. 208Pb + X 209Bi + X 238U + X 53K 59Sc 63V 67Mn 73Co 72Fe 66Cr 62Ti 58Ca 52Ar 45Cl 39P 35Al 31Na 25F Up, up and away Picture from S. Hofmann

  18. X + 132Sn N=82 Start from the beam: 132Sn

  19. Promising • The combination of N=82 targets and doubly magic 132Sn should be favourable. • Unfortunately they have the highest Coulomb barriers  • Lots of angular momentum 

  20. High spin states in SHE 48Ca + 208Pb  256No* Ex = 21 MeV 92Kr + 164Dy  256No* Ex = 24 MeV Egido & Robledo PRL 85 1198

  21. Nuclear Identification • Alpha tagging Easy, unique • Beta Tagging Tricky, need gamma • Fission Tagging Easy, not unique • Isomer Tagging Low Efficiency, Unique

  22. Equipment • Target • High beam quality needed • Prompt Spectrometer capable of high rate EXOGAM, AGATA • Separator with large transmission gas-filled Separator needed for EURISOL • Excellent Recoil ID • DAQ capable of high rate: Triggerless, Digital

  23. Gamma Ray Spectrometer • Dominant channel is constant ~0.1 - 1b Fission. This limits Ge rate! • Target wheel spokes need beam sweeping • High granularity and large distance to keep individual rates low (AGATA!) • Background from entrance windows etc. • Need windowless system!

  24. AGATA(Advanced GAmma Tracking Array) 4-array for Nuclear Physics Experiments at European accelerators providing radioactive and high-intensity stable beams Main features of AGATA Efficiency: 40% (M=1) 25% (M =30) today’s arrays ~10% (gain ~4) 5% (gain ~1000) Peak/Total: 55% (M=1) 45% (M=30) today ~55% 40% Angular Resolution:~1º  FWHM (1 MeV, v/c=50%) ~ 6 keV !!! today ~40 keV Rates: 3 MHz (M=1) 300 kHz (M=30) today 1 MHz 20 kHz • 180 large volume 36-fold segmented Ge crystals in 60 triple-clusters • Digital electronics and sophisticated Pulse Shape Analysis algorithms allow • Operation of Ge detectors in position sensitive mode  -ray tracking

  25. Electron Spectrometer • Fission does not readily produce CE • SHE produce more CE than Gamma • Delta electrons require HV barrier • Generally difficult • Rate concentrated near field axis • Baseline dirty -> need digital cards

  26. SACRED At present, electron experiments Use 20% of the beam current of Gamma experiments. Rate adjustable with HV barrier. Targets need to be thinner (0.25 mg/cm2) P.A. Butler et al., NIM A 381, 433 (1996) H. Kankanpaa et al., NIM A 534, 503 (2004)

  27. SAGE

  28. Fermium Wins Heavyweight Title E [cm-1] IP 52400 Excimer Laser l=351 + 353 nm Resonance Ionization Spectroscopy at Trans-Fermium Elements 25100 Dye Laser l=398 nm 0 GSI MAFF @ Laser Z=102 SHIP Buffer Gas Cell 25 April 2003 • Observation and Assignment of Atomic Levels without any Previous Knowledge of the Atomic Structure • Demonstrated with a Sample of 1010 Atoms255Fm, t1/2= 20.1 h, Produced at the HFIR, Oak Ridge • Based on State-of-the-Art MCDF Calculations MCDF Calculation Experiment Sewtz et al., Phys. Rev. Lett., 90 (2003) 163002-1

  29. Determination of the Atomic Structure of the Heaviest Elements J.P. Desclaux At. Data Nucl. Data Tables 12, 311 (1973) M. Sewtz, et al. • Relativistic Effects : • Contraction of thes1/2, p1/2 Orbitals • Expansion of thed,f Orbitals o Variations in Atomic and Chemical Properties • Determination of • the Valence ElectronConfiguration • by Ion Mobility Measurements~ eV • Atomic Levels / Ionization Potentialsby Optical Spectroscopy~ meV o Sewtz et al., Spectrochim. Acta B 58, 1077 (2003) ( ) @ MLLTRAP SHIPTRAP

  30. Conclusions • In-beam studies will need to be assessed individually but will be possible • Decay Spectroscopy is vital • Optical Spectroscopy provides complementary information • Exciting Times!

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