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Structure effects in the reactions 9,10,11 Be+ 64 Zn at the Coulomb barrier

Structure effects in the reactions 9,10,11 Be+ 64 Zn at the Coulomb barrier. Valentina Scuderi. 10th International Spring Seminar on Nuclear Physics, New Quest in Nuclear Structure, Vietri sul Mare, May 21-25, 2010. Reactions with neutron halo nuclei. Characteristics of the projectiles:

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Structure effects in the reactions 9,10,11 Be+ 64 Zn at the Coulomb barrier

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  1. Structure effects in the reactions 9,10,11Be+64Zn at the Coulomb barrier Valentina Scuderi 10th International Spring Seminar on Nuclear Physics, New Quest in Nuclear Structure, Vietrisul Mare, May 21-25, 2010

  2. Reactions with neutron halo nuclei Characteristics of the projectiles: Low break-up energy thresholds + long tail in density distribution Effects on fusion cross-section: Extended tails  enhancement of sub-barrier fusion Effects on direct reaction processes: Direct mechanisms, transfer and breakup, are favoured? Which is the effect of the break-up couplings on other channels ? • Elastic scattering: a fundamental tool to investigate • halo structure • influence of break-up channel • nuclear potential between the colliding nuclei

  3. Some results with 6He beam Most of the experiments performed with 6He beams (e.g. 6He+209Bi, 6He+238U, 6He+64Zn, 6He+63Cu, 6He+197Au,6He+208Pb) 4,6He+64Zn Elastic scattering a. d. @ Ecm= 12.4 MeV σReac(6He) >> σReac(4He) 6He+64Zn  particle a. d. @ Ecm=12.4 MeV T+bu ≈ 1.2b tran+bu/Reac 80% See also: E.F. Aguilera Phys. Rev. C 63 (2001) 061603, J.J. Kolata et al. Phys. Rev C 75 (2007)‏ 031302R, P. A. De Young et al. Phys. Rev. C 71 (2005)051601(R), A. Chatterjee et al. PRL 101 (2008) 032701. 3 A. Di Pietro et al. Phys.Rev.C 69(2004)044613

  4. Experiments with 11Be beam 11Be + 209Bi elastic scattering angular distributions Mazzocco et al. Eur. Phys. J. Special Topics 150 (2007) 37 No effect on the reaction cross-section in 11Be case compared with 9Be. sReac(9Be) ≈ sReac(11Be)

  5. The 9,10,11Be+64Zn experiments • Aims of the experiments: • Elastic scattering angular distribution • 11Be transfer/break-up angular distribution. 11Be ISOL beam @ ELAB = 29.8 MeV 10Be ISOL beam @ ELAB = 29.4 MeV 9Be beam @ ELAB = 29.0 MeV 9,10,11Be + 64Zn @ sameEcm = 24.5 MeV

  6. 9Be + 64Zn experiment @ LNS (Catania) 5 Si –Si detectortelescopes: ΔE: 6-15 μm thick, Si Surface Barrier detectors E : 90-130 μm thick, Si Surface Barrier detectors Angular distribution: 15° lab 110° Detectors inside the chamber

  7. 10,11Be + 64Zn experiment @ REX-ISOLDE (CERN)‏ 6 Si-Si detector telescopes: ΔE: 50 μm thick, 50x50mm2 active area DSSDs detectors 16 +16 strips (256 pixels each detector) E : 1500 μm thick, 50x50mm2 active area Si Single Pad detector Total covered angular range 10°  lab150° DSSDs Detectors inside the chamber view from the top Beam

  8. 9,10,11Be + 64Zn elastic scattering angular distributions 9Be+64Zn OM Fit 10Be+64Zn OM Fit 11Be+64Zn OM Fit • Optical Model analysis: • 9,10Be: Wood-Saxon (W-S) form for real and imaginary volume potential • 11Be: volume real and imaginary W-S potentials obtained from 10Be scattering • + • surface imaginary term • a very large diffuseness (asi=3.5fm) is needed to reproduce the elastic cross-section behaviour

  9. Reaction cross-section 9Be+64Zn OM Fit 10Be+64Zn OM Fit 11Be+64Zn OM Fit sReac(9Be) = 1090 ± 50 mb; sReac(10Be) = 1260 ± 280 mb sReac(11Be) = 2730 ± 300 mb

  10. Which processes are contributing to the large reaction cross-section in the 11Be case? 10Be+ 64Zn ∆E-E scatter plot @ 35° 11Be + 64Zn ∆E-E scatter plot @ 35° ∆E (MeV) 10Be E (MeV) ∆E (MeV) 10Be 11Be E (MeV)

  11. 11Be+64Zn transfer+break-up angular distribution tran+bu= 1100 ± 110 mb tran+bu/Reac 0.4

  12. Conclusions The collisions 9,10,11Be + 64Zn have been studied at Ecm= 24.5 MeV by using post-accelerated 10,11Be beams at REX-ISOLDE. Damping of elastic cross-section for the reaction induced by the 11Be nucleus when compared with both 9Be (Sn= 1.67 MeV) and 10Be (Sn= 6.8 MeV). Surface term with large diffuseness needed to fit the 11Be data. The reaction cross-section for 11Be induced collision is much larger than for the other two Be isotopes σReac(11Be) ~ 2 σReac(9,10Be). Evidence for the presence of a large yield of transfer and/or breakup events in the 11Be induced collision with a corresponding cross section σtran+bu ~ 1 barn. These results show a strong effect on nuclear reaction mechanisms around the Coulomb barrier due to the halo structure and its weak binding

  13. Collaboration • L. Acosta, F. Amorini, M.J.G. Borge, A. Di Pietro, P. Figuera, M. Fisichella, L.M. Fraile, J. Gòmez-Camacho, H. Jeppesen, M. Lattuada, I. Martel, M. Milin, A. Musumarra, M. Papa, M.G. Pellegriti, R.Raabe, G.Randisi, F. Rizzo, D. Santonocito, E.M.R. Sanchez, G. Scalia, V. Scuderi, O. Tengblad, D. Torresi, A.M. Vidal, M. Zadro • INFN- Laboratori Nazionali del Sud and sezione di Catania, Catania, Italy • Dipartimento di Fisica ed Astronomia, Università di Catania, Catania, Italy • Departamento de FísicaAplicada, Universidad de Huelva, Huelva, Spain • Insto. de Estructura de la Materia, CSIC, Madrid, Spain • CERN, Geneva, Switzerland • Departamento de FísicaAtómica, MolecularyNuclear, Universidad de Sevilla, Spain • RuđerBoŝkovićInstitute, Zagreb, Croatia • Dipartimento di Metodologie Fisiche e Chimiche per l’Ingegneria, Università di Catania, Catania, Italy • DAPNIA/SPhN, CE Saclay, Gif-sur-Yvette • LPC Caen, ENSICAEN, Université de Caen, CNRS/IN2P3, Caen, France

  14. Thank you

  15. 9,10,11Be+64Zn optical potentials

  16. Detector geometrydetermination Rutherford scattering for 12C + 197Au @ 28 MeV and 10Be + 197Au @ 29.4 MeV to cross check the geometry determination.  0.1

  17. 11Be+64Zn quasi-elastic angular distribution inelastic = 275  76mb

  18. Fusion cross-section measurement for 10,11Be+64Zn using the activation technique E.R. T1/2 72Se 8.4d 71Se 4.7m 72As 25h 71As 65.28h 71Ge 11.43d 69Ge 39.05h 68Ge 270.8d 68Ga 67.61m 10Be+64Zn 10Be+64Zn X-ray spectra analysis shortly after the end of the irradiation Ge isotope activity curve Work is in progress to extract fus(E) for the 10Be+64Zn systems

  19. 11Be Counts E(MeV)‏ Experiments with 11Be beam Fragmentation beam degraded to barrier energies large beam energy spread 11Be + 209Bi quasi-elastic scattering angular distributions sTR(9Be) ≈ sTR(11Be) 11Be beam energy profile No effect on the total reaction cross-section in 11Be case compared with 9Be. Mazzocco et al. Eur. Phys. J. Special Topics 150 (2007) 37

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