Abstract
The three-body breakup is studied experimentally, using a secondary 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 and for inelastic nuclear or electromagnetic excitations into the continuum are presented. The 1-strength distribution is deduced from electromagnetic cross sections and is found to exhaust of the energy-weighted Thomas-Reiche-Kuhn sum rule or 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 core and the two valence neutrons of fm is derived. The known (1.80 MeV) resonance in is observed in nuclear inelastic scattering; model-dependent values of the quadrupole deformation parameter fm or are derived. No clear signature could be obtained for predicted higher-lying 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 system are investigated. The astrophysical relevance of the data with regard to the two-neutron capture process is briefly discussed.
- Received 27 October 1998
DOI:https://doi.org/10.1103/PhysRevC.59.1252
©1999 American Physical Society