Relativistic Coulomb Excitation: from RISING to PreSPEC

1. Relativistic Coulomb Excitation: from RISING to PreSPEC • Outline • Rare ISotope INvestigation at GSI • Coulomb excitation experiments at relativistic energies • PreSPEC & AGATA • Characteristic CE parameters • Experimental conditions for relativistic CE • Feasibility studies for future experiments • Multi-step excitations • Investigation of symmetries • M1 & E2 excitations • Hans-Jürgen Wollersheim • GSI Helmholtzzentrum für Schwerionenforschung • for the PreSPEC Collaboration

2. Rare ISotope INvestigation at GSI • The Accelerators: • UNILAC(injector) - E<15 AMeV • SIS– E<2 AGeV • HI beams ranging up to 238U • Beam Currents: 109 - 1010 pps • FRS → secondary radioactive ion beams: • Fragmentation or fission of primary beams • High secondary beam energies (100 -700 AMeV) • Fully stripped ions • Reactions on a secondary target • Implantation inside a stopper • Nuclear structure of exotic nuclei • studied bysecondary fragmentation • and relativistic Coulomb excitation • g-factor measurements • Isomeric γ- and β-decay studies

3. Fast beam campaign (2003-2005) g-factor campaign (2005) Stopped beam campaign (2006-2009) Rare ISotope INvestigation at GSI EUROBALL Cluster Detectors beam tracking system • FRS: excellent spectrometer with in-flight • A and Z selection • energy resolution: ~ 1 GeV • EUROBALL:excellent γ-ray spectrometer • intrinsic energy resolution: ~ 2 keV 131Sn 132Sn + Miniball – Hector

4. Rare ISotope INvestigation at GSI EUROBALL Cluster DetectorsMiniball: HPGe segmented detectors HECTOR Large 14.5 x 17 cm BaF2 Detectors beam CATE : ΔE-E telescope event by event beam identification Coulomb Excitation at Relativistic Energy • New Shell structure at N>>Z • Relativistic Coulomb excitation of nuclei near 100Sn • Triaxiality in even-even core nuclei of N=75 isotones • E1 Collectivity in neutron rich nuclei 68Ni

5. Relativistic Coulomb Excitation of 54,56,58Cr → 197Au Identification before the secondary target after secondary target γ-efficiency = 2.8% , ΔEγ = 1.6%(1.3MeV, d=70cm)

6. for with Doppler Effect Doppler Broadening Δ

7. for Doppler Effect Doppler Broadening Δβ

8. for Doppler Effect Doppler Broadening Δβ DSAM lifetime method Velocity distribution at the moment of a prompt γ-ray decay after the production of 36Ca. (E=130 AMeV and different 9Be target thicknesses) P. Doornenbal et al. Nucl.Instr.Meth. A613 (2010), 218

9. Detector at rear LYCCA Beam Direction PreSPEC and AGATA S2´-configuration: 10 AGATA Triple Cluster + 5 double Cluster detectors γ-efficiency = 17.5% γγ-efficiency = 2.5% 10 ATC + 5 double Cluster detectors beam pipe diameter = 12cm chamber diameter = 46 cm

10. 100 AMeV r Coulomb excitation of exotic nuclei basic concepts • Inter-nuclear potential • Two forces: • Coulomb force (long range, repulsive) • Nuclear force (short range, attractive) • Potential barrier due to the compensation between the two • (Coulomb barrier) V below Coulomb barrier r Nuclear half-density radius of a Fermi mass distribution: with Mapping energy to radial separation

11. particle 100 AMeV wave • Sommerfeld parameter: • >> 1 requirement for a (semi-) classical treatment of equations of motion (hyperbolic trajectories ) Validity of classical Coulomb trajectories basic concepts η calculated at 100AMeV

12. 100 AMeV Classical Coulomb trajectories basic concepts • distance of closest approach: • impact parameter: • angular momentum : Hyperbolic trajectory: ε = sin-1(θcm/2) eccentricity of orbit

13. 100 AMeV Nuclear interaction radius σtotal = σel + σinel + σreaction σtotal ≈ σinel + σreaction Nuclear interaction radius: CP, CT half-density radii nuclear absorption:

14. 100 AMeV ‘Safe‘ bombarding energy requirement Nuclear interaction radius: CP, CT half-density radii Pure Coulomb excitation requires a much larger distancebetween the nuclei ”safe energy” requirement

15. 100 AMeV ‘Safe‘ bombarding energy requirement Dmin < 1% deviation from Coulomb excitation Rutherford scattering only if Dmin is large compared to nuclear radii + surfaces: CP, CT half-density radii choose adequate beam energy (D > Dmin for all )low-energy Coulomb excitation limit scattering angle, i.e. select impact parameter b > Dminhigh-energy Coulomb excitation

16. 100 AMeV Coulomb excitation of exotic nuclei • Electromagnetic interaction acting between two colliding nuclei. • Inelastic scattering: kinetic energy is transferred into nuclear excitation energy • Monopole-multipole interaction • Target and projectile excitation possible Excitation probability (or inelastic cross section) is a measure of the collectivityof the nuclear state of interest

17. straight line approximation 100 AMeV High-energy Coulomb excitation straight line approximation • distance of closest approach: • impact parameter: • straight line for large Ecm: b = D zero degree detector LYCCA TOF s = 3.1 m ΔE E Lund York Cologne CAlorimeter

18. D b=5.2 fm High-energy Coulomb excitation grazing angle and angular coverage of LYCCA • distance of closest approach: For nonrelativistic projectiles: at 100 MeV/u grazing angle (mrad) For relativistic projectiles ( ): Coulomb excitation: projectile mass number A1

19. Neutrons Protons High-energy Coulomb excitation grazing angle 136Xe on 208Pb at 700 MeV/u excitation of giant dipole resonance Coulomb ex. For relativistic projectiles ( ): π ν A.Grünschloß et al., Phys. Rev. C60 051601 (1999)

20. High-energy Coulomb excitation angular momentum transfer Excitation occurs only if nuclear (rotational) period is long compared to the collision time: „sudden approximation“if >> ~ 10-22 s ξ measures suddenness of interaction qmeasures strength maximum angular momentum transfer VC

21. High-energy Coulomb excitation angular momentum transfer Excitation occurs only if nuclear (rotational) period is long compared to the collision time: „sudden approximation“if >> ~ 10-22 s ξ measures suddenness of interaction qmeasures strength maximum angular momentum transfer

22. High-energy Coulomb excitation energy transfer ξ measures suddenness of interaction „adiabatic limit“ for (single-step) excitationξ=1 maximum energy transfer: VC

23. High-energy Coulomb excitation excitation energy and angular momentum transfer VC VC energy transfer (for single-step excitation): angular momentum transfer:

24. High-energy Coulomb excitation triaxiality in even-even nuclei (N=76) 21+→0+ 22+→21+ 22+→0+ 22+→21+ 22+→0+ • First observation of a second excited 2+ state populated in a Coulomb experiment at 100 AMeV using EUROBALL and MINIBALL Ge-detectors. • shape symmetry • collective strength T.R. Saito et al. Phys.Lett. B669 (2008), 19

25. J J K=0 Kmax Symmetries of the Intrinsic Hamiltonian: axial symmetry, reflection-symmetric K = angular momentum projection on symmetry axis 31y P: parity (reflection) R: rotation by 1800 T: time reversal P: parity (reflection) RT: rotation by 1800 AND time reversal (which reverses K) Production of isomeric beams: 178Hf abrasion ablation high-K orbitals near the Fermi surface E. Lubkiewicz et al. Z. Phys. A355 (1996), 191

26. Symmetries of the Intrinsic Hamiltonian: axial symmetry, reflection-asymmetric K = angular momentum projection on symmetry axis 226Ra 226Ra RP: rotation & reflection T: time reversal RPT: need all three operations In a nucleus with octupole deformation, the center of mass and center of charge tend to separate, creating a non-zero electric dipole moment. H.J. Wollersheim et al. Nucl. Phys. A556 (1993), 261

27. High-energy Coulomb excitation cross sections for E1, E2 and E3 excitations *10 • Conclusion: • The lower multipolarities are dominant 136Xe → 208Pb

28. Coulomb excitation M1 and E2 excitations, full analytical description • Conclusion: • The lower multipolarities are dominant • For a given multipole order, electric transitions • are more likely than magnetic transitions K. Alder et al., RMP 28 (56) 432

29. 1p1/2 j< = ℓ-½ Unique signature!!! 1p (ℓ=1) B(M1;j>j<)  1 N2 j> = ℓ+½ 1p3/2 High-energy Coulomb excitation M1 and E2 excitations p1/2 ??? 89Y 87Rb 83As 85Br N=50 85Br → 197Au at 100 MeV/u rate =105 s-1· 1021 cm-2 · 0.5·10-27 cm2 · 10% = 22 h-1

30. First Fast-Beam PreSPEC Proposals • Neutron-deficient sd-shell nuclei and mirror symmetry at the proton drip line: 25Si, 29S and 33Ar • Proposal by P. Reiter, M.A. Bentley, D. Rudolph • Coulomb excitation of 104Sn • Proposal by M. Gorska, J. Cederkall • Mixed-symmetry states and Coulomb excitation of 88Kr • Proposal by J. Jolie, N. Marginean

31. Call for Fast-Beam PreSPEC Proposals • AGATA Physics Workshop 2010 (AGATA@GSI) • 4-7 May 2010 Istanbul, TURKEY • 30 LOI´s for fast-beam campaign • Relativistic Coulomb excitation • B(E2)-values • lifetimes (DSAM, RDDS) • g-factor (high-velocity transient field technique) • Fragmentation reactions • lifetimes (DSAM, RDDS) • Proton scattering (LH2 target) • spectroscopic factors Recoil-Distance Doppler-Shift Method

32. PreSPEC Fast-Beam Campaign great perspectives … LYCCA-0 provides mass resolution up to A ≈ 100 AGATA increases -sensitivity ≈ 10x SIS/FRS intensities increase up to ≈ 10x PreSPEC Fast Beam Campaign convener: M. Bentley Very attractive and competitive spectroscopy themes Tracking det. and EDAQ upgrade increase max. rate and throughput 10x Unique combination of beams, set-up and people