Unusual features of proton and α-spectra from low-energy heavy-ion reactions

Abstract

Proton and α-particle spectra have been measured in low-energy 12C and 16O-induced reactions on Nb and Y targets with the primary aim of measuring the excitation energy and angular momentum dependence of nuclear level density. In the γ-multiplicity gated spectra, an unusual feature of a broad structure at high particle energies is observed in all the cases. In the case of proton spectra, the structures have compound nuclear origin and point towards an excitation energy and angular momentum-dependent enhancement which is beyond the conventional level density prescription. The broad structures in the α-spectra cannot be fully explained within the statistical model even with the enhanced level density. In this case, other reaction mechanisms like the transfer of α or 8Be to the target could also be important.