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Dipole Strengths in 112,120 Sn and

RCNP OSAKA. TECNISCHE UNIVERSITÄT DARMSTADT. Dipole Strengths in 112,120 Sn and Systematics of the Pygmy Dipole Resonance at Z=50 Shell Closure. BANU ÖZEL 1,2 , J. ENDERS 1 , Y. KALMYKOV 1 , P. von NEUMANN-COSEL 1 , A. RICHTER 1 , D. SAVRAN 1 and A. ZILGES 1

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Dipole Strengths in 112,120 Sn and

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  1. RCNP OSAKA TECNISCHE UNIVERSITÄT DARMSTADT Dipole Strengths in 112,120Sn and Systematics of the Pygmy Dipole Resonance at Z=50 Shell Closure BANU ÖZEL1,2, J. ENDERS1, Y. KALMYKOV1, P. von NEUMANN-COSEL1, A. RICHTER1, D. SAVRAN1 and A. ZILGES1 1 Institut für Kernphysics, Tecnische Universität Darmstadt, Germany 2 Cukurova University, Turkey

  2. Introduction Experimental Setup Analysis and Results Comparison with Theory Summary

  3. Darmstadt University of Technology Institute for Nuclear Physics

  4. S-DALINAC

  5. Layout of the S-DALINAC

  6. Dipole excitations in nuclei neutron proton x Giant Dipole Resonance neutron skin Pygmy Dipole Resonance N≈Z core Two Phonon State

  7. 120Sn STABLE 32.58% 116Sn STABLE 14.54% 132Sn 39.7 S  - 112Sn STABLE 0.97% 124Sn STABLE 5.79% 130Sn 3.72 M  - Systematics of the PDR in the Sn Isotope Chain There are many theoretical calculations N. Tsoneva et al. , NPA 731 (2004) 273 D. Sardi et al. , PLB 601 (2004) 27 N. Paar et al., PLB 606 (2005) 288 J. Piekarewicz, PRC 73 (2006) 044325 S. P. Kamerdizhiev, S. F. Kovaloo, PAN 65 (2006) 418 J. Terasaki, J. Engel, PRC 74 (2006) 044325 E. Litvinova et al., PLB 647 (2007) 111 Experimental data in stable and unstable Sn isotopes available Darmstadt Gent GSI Nuclear Resonance Fluorescence Coulomb Dissociation

  8. Real photon experiments at the S-DALINAC

  9. NRF Setup

  10. Spectra

  11. 90 130 =2 =1 Angular Distribution

  12. Photon Flux

  13. Photon Flux with 11B

  14. Extracted B(E1) Strengths • B(E1) 10-3 e2 fm2 174 (26) 165 (34)

  15. E1 Strength Distributions in Stable Sn Isotopes • B(E1) 10-3 e2 fm2 174(26) 233 (28) 165 (34) 379 (43)

  16. Comparison with Theory: Fragmentation

  17. Comparion with Theory: Centroid and Cumulative Strength Note: (,´) measures strength below threshold only Coulomb dissociation measures strength above threshold only

  18. Comparison with Theory: Cumulative Strengths • No simple dependence on neutron excess (or N/Z ratio)

  19. Unresolved Strength in the Background Is there unresolved strength in background? • Applicable in region where  D  > E • Level density from models Fluctuation Analysis J. Enders et al., PRL 79 (1997) 2010 T. Rauscher et al., PRC 56 (1997) 1613 BSFG1 T. von Egidy and D. Bucurescu, PRC 72 (2005) 044311 BSFG2 P. Demetriou and S. Goriely, NPA 695 (2001) 95 HF-BCS

  20. Unresolved Strength in the Background PRELIMINARY

  21. Summary • Systematic of PDR in stable Sn isotopes established • Models close to results either in stable or in unstable nuclei, but not • both • No simple dependence of total strength on neutron excess • We need measurements across the neutron threshold • NEPTUN tagger at S-DALINAC • High resolution (p,p´) at 0o at RCNP

  22. Thanks TU Darmstadt U. of Giessen U. of Zagreb A. Richter, P. von Neumann-Cosel, J. Enders, Y. Kalmykov, V. Ponomarev, I. Poltoratska D. Savran, A. Zilges H. Lenske, N.Tsoneva, N. Paar, Florida SU J. Piekarewicz, Thanks to RCNP and Prof. Dr. Atsushi Tamii

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