Search for high excitation energy structures inZr90andPb208, viaNe20inelastic scattering

The inelastic scattering of ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ on ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$ and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ has been studied at 500 and 600 MeV incident energies. High statistics spectra were measured at the grazing angle. For each target, spectra at the two incident energies were compared by means of cross correlation analysis. Structures were observed in the inelastic spectra, but they appeared at different excitation energies at the two beam energies and therefore cannot be identified with high-excitation energy states of the target nuclei in contradiction to the results of previous experiments. Rather they arise from the decay of discrete unbound states in the projectile-like nuclei which were excited by a one-nucleon-transfer reaction. In particular, the structures observed in the transfer-evaporation continuum of the ${}_{}{}^{20}{}_{}{}^{}$Ne${+\mathrm{}}^{208}$Pb spectra appear to be mainly due to neutron emission from known discrete unbound states in ${}_{}{}^{21}{}_{}{}^{}\mathrm{Ne}$. A relatively low upper limit is given for the production cross section of multiphonon states in these systems.