Structure in multiplicity gated proton spectra in low energy 12C + 93Nb reaction—compound nuclear process or massive cluster transfer?

Gamma multiplicity gated proton spectra have been measured in the 12C + 93Nb reaction at E(C12)=40MeV at backward angles. The shape of the spectrum shows a drastic change with the increase in multiplicity acquiring a broad structure at proton energies beyond ∼15MeV corroborating our earlier measurements at E(C12)=42.5MeV. Measurements made in coincidence with residue γ rays, detected in an array of eight HPGe clover detectors, confirm these observations. An excitation energy and angular momentum-dependent enhancement of the nuclear level density or a massive cluster transfer of 11B to the 93Nb can explain the data.