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The compound nucleus 76Kr* was populated at the excitation energy of 75 MeV and angular momentum of 39 h in fusion reactions with two complementary, mass-symmetric (31P+45Sc) and mass asymmetric (12C+64Zn) entrance channels. The neutron evaporation spectra were measured and compared with the predictions of the statistical model calculations. The results for the mass-asymmetric reaction are found to be consistent with the predictions of the statistical model calculations. However, for the mass-symmetric reaction (31P+45Sc), the experimental spectra are found to be harder than the theoretical neutron spectra. The dynamical model calculations of Feldmeier show that the formation time for the compound nucleus for the symmetric system is relatively larger as compared to the asymmetric system. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

The compound nucleus 76Kr* is formed in the heavy-ion fusion reactions by an asymmetric entrance channel 12C+64Zn and the symmetric entrance channel 31P+45Sc at the excitation energy of 75 MeV and angular momentum of 39 h. Neutron energy spectra of the asymmetric system (12C+64Zn) at different angles are well described by the statistical model predictions using the normal value of the level density parameter a = A/8 MeV -1. However, in the case of the symmetric system (31P+45Sc), the statistical model interpretation of the data requires the change in the value of a = A/10 MeV-1. The delayed evolution of the compound system in case of the symmetric 31P+45Sc system may lead to the formation of a temperature equilibrated dinuclear complex, which may be responsible for the neutron emission at higher temperature, while the protons and alpha particles are evaporated after neutron emission when the system is sufficiently cooled down and the higher ℓ-values do not contribute in the formation of the compound nucleus for the symmetric entrance channel in case of charged particle emission. [ABSTRACT FROM AUTHOR]