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

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

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

4. Norbert Pietralla Isolde WS2007 Simple Example: Harmonic Oscillator, N=2 E 2+n2+n 2+12+1 2 + ms 2+p2+p V pn

5. Norbert Pietralla Isolde WS2007 Experimental signature for MSSs: M1 transitions g   1  N, g  0  N M1 forbidden between FSSs! LL L

6. Norbert Pietralla Isolde WS2007 Richter, Kneissl, von Brentano et al. Sensitivity to Shell Structure MSSs at the analytical Limits N  = N =1 Status of MS structures in vibrational nuclei M1 phenomena in the valence shell E2M1 Scissors mode Measure of quadrupole collectivity 2+2+ 0+0+ 2+2+ 4+4+ 0+0+ 2+2+ SU(3) Rotor 2+2+ 3+3+ 1+1+ Scissors Mode A. Richter et al. TU Darmstadt, 1983 K=1 Stuttgart-Darmstadt-Köln 1+1+ 0+0+ 4+4+ 2+2+ 0+0+ 2+2+ 2+2+ 1+1+ 3+3+ U(5) Vibrator F max -1 MS multi-Phonon structure N. Pietralla et al., PRC 58, 184 (1998)

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

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

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

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

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

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

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

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

15. Norbert Pietralla Isolde WS2007 Inverse kinematics CoulEx to MSSs at ANL carbon G.Rainovski, NP et al, PRL 96 122501 (2006) 138 Ce Coulomb excitation Detector array Study pn-symmetry in valence shell REX-Isolde, HRIBF, CARIBU,… exotic nuclei 138 Ce@480MeV 788 (2 + 1 →0 + ) 1448 (2 + ms →2 + 1 ) 2237 (2 + ms →0 + 1 ) M1 E2 gs 2 + ms 2+12+1

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

17. Norbert Pietralla Isolde WS2007  = 1.204(33)ps  = 180(9)fs  = 82(5)fs  = 156(10)fs  = 91(36)fs The population cross-sections at 480 MeV CLX code (H. Ower – J. Gerl – H. Scheit) Based on Multiple step Coulex theory (Winter – de Boer) B(E2, 2 1 + )↑= 0.450(30) e 2 b 2 B( , J j + )  BR CLX + Radiation character from angular distribution

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

19. Norbert Pietralla Isolde WS2007 Two-Level Mixing  2 = B(M1;2 + 4  2 + 1 )/ B(M1;tot) = 0.12/0.18 = 0.7 V F-mix = 44(3) keV => “shell stabilization of MS structures” 0.18 0.12 0.06

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

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

22. Norbert Pietralla Isolde WS2007 Direct evidence for p-n interaction V pn in the valence shell Energy splitting increases with growing valence shell (increasing N p ) Task for Radioactive Beam Accelerators (e.g. HRIBF, REXIsolde…) Proton Number Z 2+12+1 One phonon 2 + evolution in N=80 isotones 2+22+2 132 Te 2 + ms V pn ~ (N p N n ) 1/2 E 2+n2+n 2+12+1 2 + ms 2+p2+p V pn

23. Norbert Pietralla Isolde WS2007 What RIB intensity needed for studying MSSs? 15 h at 6.10 9 pps! 1/25 1/250 1/2500 10 7 pps for 2 weeks 10 6 pps for 2 weeks 10 5 pps for 2 weeks To identify excited 2 + state (beyond the 2 + 1 ) in vibrational nucleus (B(E2)~1Wu) with Gammasphere for 2 weeks beam time we need 10 5 pps. For complete spectroscopy 10 6 -10 7 pps will be needed! 2 + ms

24. Norbert Pietralla Isolde WS2007 Outlook (e,e’)  transition densities for p and n Trace evolution of V p-n RIBS  exotic nuclei  HRIBF, ANL CARIBU, REX-ISOLDE, SPIRAL II, … Proton Number Z 2+12+1 2 + ms 2 + evolution in N=80 isotones 132 Te 140 Xe 4 + 140 Xe 2 + FWHM ~9 keV R. Kruecken et al. Munich (2006) MINIBALL @ CERN REX-ISOLDE 510 5 part/sec

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