On the interpretation of evaporation residue mass distributions in heavy-ion induced fusion reactions

Evaporation residue mass distributions measured recently for several heavy-ion induced fusion reactions are analyzed. The reactions investigated are ¹⁹F on ¹²C (E_lab = 50, 63 and 76 MeV), ¹⁹F on ²⁷Al (E_{lab = 40}, 63, 76 and 92 MeV) and ¹⁶O on ²⁷Al (E_{lab = 30}, 40, 60 and 80 MeV). Starting from the assumption that a compound nucleus is formed which decays by multiple emission of neutrons, protons, α-particles and γ-rays with probabilities as predicted by the statistical theory the mass spectra of the stable or long-lived products are calculated. It is shown that they are in good agreement with the experimental data, if reasonable assumptions are made about the level densities and the shape of the yrast line. The possibility to use these methods for studying the properties of highly excited nuclei at high angular momentum is investigated.