1 / 23

Nuclear Mixed-Symmetry States as Probe for pn Effective Valence Shell Interaction

Explore mixed symmetry states in nuclear physics, examine effective valence shell interaction, and investigate collective isovector valence shell excitations. Study quantum system collectivity, isospin symmetry, and shell structure with focus on M1 and E2 transitions. Review experimental signatures and sensitivity to shell structure with systematic calculations. Learn about coulomb excitation experiments, electron scattering, and transition strength distributions for characterizing mixed symmetry structures in vibrational nuclei.

dkeyser
Download Presentation

Nuclear Mixed-Symmetry States as Probe for pn Effective Valence Shell Interaction

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. SFB634 CRE Nuclear/Radiation physics Collaborators Outline Christoph Fransen Georgi Rainovski Jason Holt Nico Orce Oleksiy Burda Peter von Neumann-Cosel Volker Werner Tan Ahn ANL • Mixed Symmetry States • Recent Progress • Research with RIBs • Outlook & Summary S-DALINAC, TUD Nuclear Mixed-Symmetry States as Probe for pn Effective Valence Shell Interaction Norbert Pietralla Institut f ür Kernphysik, TU-Darmstadt Norbert Pietralla Isolde WS2007

  2. Coexist, interplay, and compete? Study collective isovector valence shellexcitations (combine all 3 aspects) Generic Aspects of NuclearStructure Heavy Atomic nucleus Two-fluid quantum system • many-body system • COLLECTIVITY • consists of two equivalent entities (protons-neutrons) • ISOSPIN SYMMETRY • quantum system • SHELL STRUCTURE Study mixed symmetry (MS) structures ! Norbert Pietralla Isolde WS2007

  3. Model pn-symmetry in valence shell IBM, analytic solutions Approximation: Contain pn-antisymmetric boson pairs Signature: enhanced M1 radiation F-spin = Isospin in Systems of “elementary” Bosons Norbert Pietralla Isolde WS2007

  4. E 2+ms 2+n Vpn 2+p 2+1 Simple Example: Harmonic Oscillator, N=2 Norbert Pietralla Isolde WS2007

  5. Experimental signature for MSSs: M1 transitions Lp Ln gp  1 N, g 0 N M1 forbidden between FSSs! Norbert Pietralla Isolde WS2007

  6. Fmax-1 SU(3) Rotor U(5) Vibrator 3+ 3+ 1+ 2+ 1+ 2+ 4+ 2+ 0+ 2+ M1 Scissors mode K=1 E2 0+ MS multi-Phonon structure 4+ Scissors Mode 2+ 2+ A. Richter et al. TU Darmstadt, 1983 0+ 0+ MSSs at the analytical Limits M1 phenomena in the valence shell Sensitivity to Shell Structure Np= N =1 Richter, Kneissl, von Brentano et al. Measure of quadrupole collectivity Stuttgart-Darmstadt-Köln 1+ 2+ • Status of MS structures in vibrational nuclei N. Pietralla et al., PRC 58, 184 (1998) Norbert Pietralla Isolde WS2007

  7. Nb 93 Mixed symmetry phonon structure at N = 52 Orce et. al (2006) Norbert Pietralla Isolde WS2007

  8. M1 strength, 2+ 2+1 Identification of multi-phonon MSSs E2 strength from g.s. Norbert Pietralla Isolde WS2007

  9. First observation of vibrational MS structure in odd-mass nuclei Doppler-shift lifetimes from (n,n‘) at Lexington 94Mo 93Nb 2+ms 1196 2+ 871 0+ B(M1)93Nb = 0.32(11)[0.62(24)]mN2 B(M1)94Mo = 0.56(5) mN2 J.N. Orce et al, PRL 97, 062504 (2006). Norbert Pietralla Isolde WS2007

  10. x Systematic SM calculations from NNinteraction with Vlow-k J. D. Holt et al, (submitted) Yale-Rutgers collaboration (preliminary) Inverse kinematics Coulomb excitation Norbert Pietralla Isolde WS2007

  11. Electron Spectrometer Program at S-DALINAC M1/g-factor = integral  one value Cross sections = differential  a function (1-dim more structure information) 130 MeV in-house electron LINAC ideal for nuclear structure studies Norbert Pietralla Isolde WS2007

  12. Electron scattering on vibrational multi-phonon MSSs Darmstadt data with O.Burda, P.von Neumann-Cosel A.Richter et al. 94Mo(e,e’) iThembaLabs data with H.Fujita P.von Neumann-Cosel et al. 94Mo(p,p’) • Ideal for one-phonon states • Sensitive to 14 lowest 2+ states Norbert Pietralla Isolde WS2007

  13. Experiment QPM IBM-2 SM (Vlow-k) 94Mo(e,e’) Form FactorsTest of quantum mechanical wavefunction IBM-2 and SM Vlow-k in good agreement with experiment. combination with hadronic probe [forward-angle (p,p’) at iThembaLabs] allows for isospin-sensitivity. Norbert Pietralla Isolde WS2007

  14. 788 (2+1→0+) carbon 138Ce@480MeV 2+ms 1448 (2+ms→2+ 1) 2237 (2+ms→0+ 1) M1 2+1 exotic nuclei E2 REX-Isolde, HRIBF, CARIBU,… gs Inverse kinematics CoulEx to MSSs at ANL Coulomb excitation 138Ce 138Ce Detector array Study pn-symmetry in valence shell G.Rainovski, NP et al, PRL 96 122501 (2006) Norbert Pietralla Isolde WS2007

  15. 2+ms CoulEx of Mixed-Symmetry States Observe 2+1,2,3,4,5,6 up to 2.7 MeV in collaboration M.P.Carpenter R.V.F.Janssens C.J.Lister S.Zhu G.Rainovski, NP et al., Phys.Rev.Lett. 96 122501 (2006). Gammasphere at ANL Norbert Pietralla Isolde WS2007

  16. B(E2, 21+)↑= 0.450(30) e2b2 t = 91(36)fs t = 156(10)fs t = 82(5)fs t = 180(9)fs t = 1.204(33)ps CLX B(l, Jj+) BR t The population cross-sections at 480 MeV + Radiation character from angular distribution CLX code (H. Ower – J. Gerl – H. Scheit) Based on Multiple step Coulex theory (Winter – de Boer) Norbert Pietralla Isolde WS2007

  17. Transition Strength Distributions E2 M1 E2 Norbert Pietralla Isolde WS2007

  18. MSS Investigation @ Argonne (“Missia”) program overview Sm Ce Ba Xe Previous literature Published Under analysis Expt accepted proposed • ANL ATLAS Superconducting LINAC • Gammasphere Chart from: http://www.nndc.bnl.gov Norbert Pietralla Isolde WS2007

  19. 2+ms 2+ms Recent Coulex Experiments November 2005 at ANL: 136Ce, 134Xe June 2006 at ANL: 124,126,128,130,132Xe (under analysis) 132Xe 134Xe Norbert Pietralla Isolde WS2007

  20. E 132Te 2+ms 2+n 2+2 Vpn ~ (NpNn)1/2 Vpn 2+p 2+1 Direct evidence for p-n interaction Vpn in the valence shell One phonon 2+ evolution in N=80 isotones 2+ms 2+1 Proton Number Z • Energy splitting increases with growing valence shell (increasing Np) Task for Radioactive Beam Accelerators (e.g. HRIBF, REXIsolde…) Norbert Pietralla Isolde WS2007

  21. What RIB intensity needed for studying MSSs? 15 h at 6.109 pps! 1/25 107pps for 2 weeks 2+ms 1/250 106pps for 2 weeks 2+ms To identify excited 2+ state (beyond the 2+1) in vibrational nucleus (B(E2)~1Wu) with Gammasphere for 2 weeks beam time we need 105pps. For complete spectroscopy 106-107 pps will be needed! 1/2500 105pps for 2 weeks Norbert Pietralla Isolde WS2007

  22. (e,e’)  transition densities for p and n Trace evolution of Vp-n RIBS  exotic nuclei HRIBF, ANL CARIBU, REX-ISOLDE, SPIRAL II, … 132Te 2+ evolution in N=80 isotones 2+ms 2+1 Proton Number Z Outlook 140Xe 2+ FWHM ~9 keV R. Kruecken et al. Munich (2006) 140Xe 4+ MINIBALL @ CERN REX-ISOLDE 5•105 part/sec Norbert Pietralla Isolde WS2007

  23. Summary • Proton-Neutron Mixed-Symmetry States are sensitive probes of the pn-interaction in the valence shell • 94Mo – a textbook example • 93Nb – first vibrational MSSs in odd-A nucleus • Advances in nuclear theory (Vlow-k for MS) • First g-factors for MSSs (92,94Zr) • New avenue in (e,e’) @ S-DALINAC • “Missia” program @ ANL • Great potential for RIBs (map Vpn in exotic regions) Norbert Pietralla Isolde WS2007

More Related