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

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

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

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

The 9,10,11 Be+ 64 Zn experiments Aims of the experiments: Elastic scattering angular distribution Elastic scattering angular distribution 11 Be transfer/break-up angular distribution. 11 Be transfer/break-up angular distribution. 11 Be ISOL E LAB = 29.8 MeV 10 Be ISOL E LAB = 29.4 MeV 9 Be E LAB = 29.0 MeV 9,10,11 Be + 64 same E cm = 24.5 MeV

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

10,11 Be + 64 Zn REX-ISOLDE (CERN)‏ Beam DSSDs Detectors inside the chamber view from the top 7 6 Si-Si detector telescopes: ΔE: 50 μm thick, 50x50mm 2 active area DSSDs detectors ΔE: 50 μm thick, 50x50mm 2 active area DSSDs detectors strips (256 pixels each detector) strips (256 pixels each detector) E : 1500 μm thick, 50x50mm 2 active area Si Single Pad detector E : 1500 μm thick, 50x50mm 2 active area Si Single Pad detector Total covered angular range 10°   lab  150° Total covered angular range 10°   lab  150°

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

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

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

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

Conclusions The collisions 9,10,11 Be + 64 Zn have been studied at E cm = 24.5 MeV by using post- accelerated 10,11 Be beams at REX-ISOLDE. Damping of elastic cross-section for the reaction induced by the 11 Be nucleus when compared with both 9 Be (S n = 1.67 MeV) and 10 Be (S n = 6.8 MeV). Surface term with large diffuseness needed to fit the 11 Be data. The reaction cross-section for 11 Be induced collision is much larger than for the other two Be isotopes σ Reac ( 11 Be) ~ 2 σ Reac ( 9,10 Be). Evidence for the presence of a large yield of transfer and/or breakup events in the 11 Be induced collision with a corresponding cross section σ tran+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

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 Física Aplicada, Universidad de Huelva, Huelva, Spain Insto. de Estructura de la Materia, CSIC, Madrid, Spain CERN, Geneva, Switzerland Departamento de Física Atómica, Moleculary Nuclear, Universidad de Sevilla, Spain Ruđer Boŝković Institute, 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 Collaboration

Thank you

15 9,10,11 Be+ 64 Zn optical potentials 9,10,11 Be+ 64 Zn optical potentials ReactionV(MeV)‏a(fm)‏ R 0 (fm)‏ V i (MeV)‏ a i (fm)‏ R i0 (fm)‏ V Si (MeV)‏ a Si (fm)‏ R Si (fm)‏ 9 Be+ 64 Zn Be+ 64 Zn Be+ 64 Zn

Rutherford scattering for 12 C MeV and 10 Be MeV to cross check the geometry determination. Detector geometry determination  0.1

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

Work is in progress to extract  fus (E) for the 10 Be+ 64 Zn systems Fusion cross-section measurement for 10,11 Be+ 64 Zn using the activation technique 10 Be+ 64 Zn X-ray spectra analysis Ge isotope activity curve shortly after the end of the irradiation E.R.T 1/2 72 Se8.4d 71 Se4.7m 72 As25h 71 As65.28h 71 Ge11.43d 69 Ge39.05h 68 Ge270.8d 68 Ga67.61m 10 Be+ 64 Zn

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