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چکیده
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A stochastic approach based on four dimensional dynamical model has been used to simulate the fission process of the excited compound nuclei 213ّFr,215Fr and 217Fr produced in fusion reactions. Effects of isospin and dissipation coefficient of the K coordinate,gk, on estimation of the evaporation residue cross section, the prescission neutron multiplicity, the variance of the mass and energy distributions of fission fragments and the anisotropy of fission fragments angular distribution have been investigated for the excited compound nuclei213ّFr,215Fr and 217Fr. Three collective shape coordinates plus the projection of total spin of the compound nucleus to the symmetry axis,k , were considered in the four dimensional dynamical model. In the four dimensional dynamical model the magnitude of the dissipation coefficient of k, gk , was considered as a free parameter and its magnitude inferred by fitting measured data on the evaporation residue cross section. Results of the extracted dissipation coefficients of K for different isotopes of Fr were shown that the magnitude of the dissipation coefficient of gk increases with decreasing isospin of fissioning compound nucleus. It was also shown that the prescission neutron multiplicity and the anisotropy of fission fragments angular distribution increase with increasing isospin whereas the variance of the mass and energy distributions of fission fragments decrease with increasing isospin of fissioning compound nucleus. Furthermore, it was shown that the calculated values of prescission neutron multiplicity and the variance of the mass distribution of fission fragments for the excited compound nuclei 213ّFr,215Fr and 217Fr decrease with the dissipation strength of k , whereas the variance of the energy distribution of fission fragments and the anisotropy of fission fragments angular distribution increase with the dissipation strength of k .
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