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Continuum excitations in 6He

AuthorsAumann, T.; Aleksandrov, D.; Axelsson, L.; Baumann, T.; García Borge, María José ; Suzuki, T.; Tengblad, Olof ; Zhukov, M. V.
Issue Date1-Mar-1999
PublisherAmerican Physical Society
CitationPhysical Review C - Nuclear Physics 59: 1252-1262 (1999)
AbstractThe three-body breakup 6He→4He+n+n is studied experimentally, using a secondary 6He ion beam of 240 MeV/nucleon incident on carbon and lead targets. Integrated cross sections for one-and two-neutron knockout and differential cross sections dσ/dE* and dσ/dv for inelastic nuclear or electromagnetic excitations into the 6He continuum are presented. The E1-strength distribution is deduced from electromagnetic cross sections and is found to exhaust (10±2)% of the energy-weighted Thomas-Reiche-Kuhn sum rule or (40±8)% of the cluster sum rule for excitation energies below 5 MeV. Both the energy-weighted and non-energy-weighted dipole cluster sum rules are almost exhausted integrating the strength up to 10 MeV, a fact from which the root-mean-square distance between the α core and the two valence neutrons of rα-2n = (3.36±0.39) fm is derived. The known IΠ=2+ (1.80 MeV) resonance in 6He is observed in nuclear inelastic scattering; model-dependent values of the quadrupole deformation parameter δ2=( 1.7 ±0.3) fm or B(E2,0+→2+ ) = (3.2±0.6)e2 fm4 are derived. No clear signature could be obtained for predicted higherlying 2+ resonances, but low-lying continuum strength of multipolarity other than dipole, likely of monopole and quadrupole multipolarity, is indicated by the data. Two-body correlations in the decaying 4He+n+n system are investigated. The astrophysical relevance of the data with regard to the two-neutron capture process 4He(2n,γ)6He is briefly discussed. ©1999 American Physical Society
DescriptionT. Aumann et al. ; 11 págs.; 6 figs.; 2 tabs. ; PACS number(s): 27.20.1n, 25.60.Gc, 25.70.De, 29.30.Hs
Publisher version (URL)https://doi.org/10.1103/PhysRevC.59.1252
Identifiersdoi: 10.1103/PhysRevC.59.1252
issn: 0556-2813
Appears in Collections:(CFMAC-IEM) Artículos
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