Inelastic scattering of20Ne and12C on58Ni and the three-body continuum

Abstract

Using beams of20Ne at 291 and 392 MeV and12C at 300 MeV the inelastic excitation of collective modes in58Ni has been studied with a Q3D magnetic spectrometer. In the analysis different contributions are unfolded from the spectra:1. single lines,2. the inelastic continuum,3. the three-body continuum, which mainly originates from one-nucleon pick-up to unbound states followed by the nucleon emission. Special care was taken to calculate the spectral shape and strength of this process. The population of unbound21Ne-states is measured in a neutron-20Ne coincidence experiment. Coupled channel calculations have been performed to extract the deformation parameters for the inelastic states, including mutual excitation. For the giant quadrupole resonance 70 % of the energy weighted sum rule is found. The excitation of higher multipoles is calculated and extrapolated to higher incident energies (50 MeV/u). The importance of the in-elastic excitation as a “doorway process” to more complex interactions is discussed. It is found that especially the excitation of the projectile (20Ne) takes a large fraction (20–50 %) of the incoming flux in the first step.