1 / 18

Structure and Reactions of Exotic Nuclei, 24-26 February 2005

N*  + 3n light nuclei via the ( 7 Li, 7 Be) reaction. Francesco Cappuzzello. Structure and Reactions of Exotic Nuclei, 24-26 February 2005. N = 1 7 He N = 2 11 Be N = 3 15 C N = 4 19 O N = 5 23 Ne

karena
Download Presentation

Structure and Reactions of Exotic Nuclei, 24-26 February 2005

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. N* + 3n light nuclei via the (7Li,7Be) reaction Francesco Cappuzzello Structure and Reactions of Exotic Nuclei, 24-26 February 2005

  2. N = 1 7He N = 2 11Be N = 3 15C N = 4 19O N = 5 23Ne N = 6 27Mg … BSEC (Bound States Embedded in the Continuum) Softer core What exactly? Hard core An important part of the phase space is represented by DCP (Dynamical Core Polarization) Systematic study via the (7Li,7Be) reaction

  3. (7Li,7Be) reaction over 7Li, 11B, 15N, 19F, 23Na, 27Al • Study of single particle isovector excitations • Problem of the core polarisation • Systematic study of the (7Li,7Be) reaction at low incident energy as function of charge asymmetry and mass References: F.Cappuzzello et al., Excited states of 11Be, Phys.Lett B516 (2001) 21 F.Cappuzzello et al., Analysis of the 11B(7Li,7Be)11Be reaction at 57 MeV in a Microscopic Approach,Nucl. Phys. A739 (2004) 30. F.Cappuzzello et al., Excited states of 15C, EuroPhys.Lett. 65 (2004) 766 C.Nociforo et al. Investigation of light neutron-rich nuclei via the (7Li,7Be) reaction, Acta Physica Polonica, B34 (2003) 2387. S.E.A. Orrigo et al. On the line shape of 15Csubmitted to Phis. Lett. B 2004

  4. 7Be detected with the IPN-Orsay Split Pole Examples: Counts DCP regime Single particle regime l = 9, 14 keV/ch. 11B(7Li,7Be)11Be at 57 MeV 11Be excitation energy (MeV) Counts Single particle regime l = 14, 55 keV/ch. 15N(7Li,7Be)15C at 55 MeV DCP regime 15C excitation energy (MeV)

  5. 7 He and19O spectra via (7Li,7Be)at 56 MeV 19F(7Li,7Be)19O Target LiF+C riv = 0°

  6. Results of microscopic QRPA calculations Single particle The strength is well reproduced for single particle transitions, namely ½+ gs, ½- excited state at 0.32 MeV and 5/2+ state at 1.77 MeV The observed fragmentation beyond 2 MeV is not reproduced

  7. Results of microscopic DWBA calculations 11Be*1.77 Direct one step mechanism No scaling factors Angular distributions reproduced withoutany scaling factor or parameter tuning 11BeGS No scaling factors

  8. Nuclear structure model Quasiparticle-core coupling model (QPC)(Bohr & Mottelson) eff. Hamiltonian of the odd-masssystem Odd-mass system w. f. : Quasiparticle-RPA approach: s.p. mixing1qp 3qp V13couples where is the g.s. correlated of the even-mass coreand byBogolyubov-Valatin transformation state-dependent mass operator with H. Lenske, Progr.in Part. and Nucl.Phys. A693(2001)616

  9. 15C response function s1/2 and d5/2 strength functions of 15C calculated with Jc3 [ g.s. configuration: 0.110 MeV excited configuration: dominance of core excitations (1-,2+,3-) Strong fragmentation of the strength for 9<Ex<15 MeV C. Nociforo, H.Lenske, in preparation

  10. Some experimental consideration Experiments need high energy resolution (1/1000), forward angles (around 0) exploration and large momentum byte (1020%) Magnetic spectrographs IPN-Orsay Split-Pole Energy resolution  1/1000 Momentum byte 36 % Solid angle  1.8 msr The small solid angle limits the possibility to study weak narrow states above neutron emission threshold

  11. The MAGNEX opportunity Large solid angle and high energy resolution A.Cunsolo et al., NIMA 481 (2002) 48 A.Cunsolo et al., NIMA 484 (2002) 56 A.Cunsolo et al., NIMA 495 (2002) 216

  12. Conclusions and outlooks • Exploration of excited states of light neutron rich nuclei is a rich source of information about nuclear structure • High energy resolution is crucial to that purpose • Use of refined microscopic theories is also fundamental • Challanges • Use of the MAGNEX spectrometer (starting from next weeks) • Full development of the microscopic DCP theory (on the run)

  13. The “Charge Exchange”collaboration  A.Cunsolo, F.C., A.Foti, A.Khouaja, C.Nociforo, S.E.A.Orrigo, J.S.Winfield, M.Cavallaro INFN-LNS, Catania, Italy INFN, Sez. Catania, Catania, Italy Dipartimento di Fisica, Università di Catania, Catania, Italy D. Beaumel, S. Fortier, Institut de Physique Nucléaire, IN2P3-CNRS, Orsay, France H.Lenske Universitatat Giessen, Giessen, Germany

  14. 15N(7Li,7Be)15C reaction at 55 MeV Counts single particleregime = 14 (55 keV/ch) DCP regime 15C excitation energy (MeV) F. Cappuzzello et al., Phys. Lett. B516, 21 (2001) C. Nociforo et al., Acta Phys. Polonica B34 ,2387 (2003) F.Cappuzzello et al., Europhys. Lett. 65, 766 (2004) F. Cappuzzello et al., Nucl. Phys. A739, 30 (2004)

  15. 15C and 11Be spectra via (7Li,7Be) at 57 MeV qlab=10° 136 keV/ch 0.74 counts 8.5 10.3 g.s. 15C Excitation Energy (MeV) 100 80 60 40 20 0 6.0 15C state at 8.49 MeV (FWHM 270±50 keV) qlab=9° 140 keV/ch counts 9.5 11Be state at 6.05 MeV (FWHM 320±40 keV) 0 2 4 6 8 10 12 14 16 11Be Excitation Energy (MeV) F.Cappuzzello et al., Phys.Lett.B516(2001)21

  16. Core excitations For large A/Z ( A-1 ) core soft Apparence of low energy (vibrational) states ( 2+ , 3- ) Evidence of 2+ core excitation in 11Beg.s. 1H(11Be,10Be) at 35.3 MeV/u 2+ J.S.Winfield et al., Nucl.Phys. A683(2001)48

  17. CEXtransitions19Fgs 19O • CEX-QRPA Bogoliubov-Valatin transformation From HFB calculations Projection over isospin τ+ subspace Average treatment of the configurations ortogonal to 2QP ones (i.e. 4QP...)

  18. CEX-QRPA (Charge EXchange Quasi-particle Random Phase Approximation) Green function approach to QRPA Need to describe effect due to the proximity of the continuum F.T.Baker et al. Phys. Rep. 289, 235 (1997) Response function Dyson Equation

More Related