Coulomb and nuclear breakup of a halo nucleus {sup 11}Be

Journal Article · Mon Nov 01 00:00:00 EST 2004 · Physical Review. C, Nuclear Physics

DOI:https://doi.org/10.1103/PhysRevC.70.054606· OSTI ID:20695749

Fukuda, N; Aoi, N; Imai, N; Ishihara, M; Kubo, T; Watanabe, Y X; Yoneda, K ^[1]; Nakamura, T ^[2]; Kobayashi, T; Otsu, H ^[3]; Iwasaki, H; Sakurai, H ^[4]; Mengoni, A ^[1]; Notani, M; Shimoura, S; Teranishi, T ^[5]

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1. RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan)
2. Department of Physics, Tokyo Institute of Technology, 2-12-1 O-Okayama, Meguro, Tokyo 152-8551 (Japan)
3. Department of Physics, Tohoku University, 2-1 Aoba, Aramaki, Aoba, Sendai 980-8578 (Japan)
4. Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033 (Japan)
5. CNS, University of Tokyo, RIKEN campus, Hirosawa 2-1, Wako, Saitama 351-0198 (Japan)

Breakup reactions of the one-neutron halo nucleus {sup 11}Be on lead and carbon targets at about 70 MeV/nucleon have been investigated at RIKEN by measuring the momentum vectors of the incident {sup 11}Be, outgoing {sup 10}Be, and neutron in coincidence. The relative energy spectra as well as the angular distributions of the {sup 10}Be+n center of mass system (inelastic angular distributions) have been extracted both for Pb and C targets. For the breakup of {sup 11}Be on Pb, the selection of forward-scattering angles, corresponding to large impact parameters, is found to be effective to extract almost purely the first-order E1 Coulomb breakup component and to exclude the nuclear contribution and higher-order Coulomb breakup components. This angle-selected energy spectrum is thus used to deduce the spectroscopic factor for the {sup 10}Be(0{sup +})x{nu}2s{sub 1/2} configuration in {sup 11}Be which is found to be 0.72{+-}0.04 with a B(E1) strength up to E{sub x}=4 MeV of 1.05{+-}0.06 e{sup 2} fm{sup 2}. The energy weighted E1 strength up to E{sub x}=4 MeV explains 70%{+-}10% of the cluster sum rule, consistent with the obtained spectroscopic factor. The non-energy-weighted sum rule within the same energy range is used to extract the root-mean-square distance of the halo neutron to be 5.77(16) fm, consistent with previously known values. In the breakup with the carbon target, we have observed the excitations to the known unbound states in {sup 11}Be at E{sub x}=1.78 MeV and E{sub x}=3.41 MeV. Angular distributions for these states show the diffraction pattern characteristic of L=2 transitions, resulting in a J{sup {pi}}=(3/2,5/2){sup +} assignment for these states. We finally find that even for the C target the E1 Coulomb direct breakup mechanism becomes dominant at very forward angles.

• OSTI ID: 20695749
• Journal Information: Physical Review. C, Nuclear Physics, Vol. 70, Issue 5; Other Information: DOI: 10.1103/PhysRevC.70.054606; (c) 2004 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2813
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ANGULAR DISTRIBUTION
BERYLLIUM 10
BERYLLIUM 11
BERYLLIUM 11 REACTIONS
BREAKUP REACTIONS
CARBON 12 TARGET
CLUSTER MODEL
DIRECT REACTIONS
E1-TRANSITIONS
ENERGY SPECTRA
EXCITATION
IMPACT PARAMETER
MEV RANGE
NEUTRONS
NUCLEAR HALOS
OPTICAL MODELS
PARITY
SPECTROSCOPIC FACTORS
SPIN
SUM RULES