PREEQUILIBRIUM FRACTION IN ALPHA-INDUCED REACTIONS FROM THRESHOLD TO 40 MEV

alpha-particle induced excitation functions for the reactions Mn-55 (a lpha, n), Cu-63 (alpha, n), Cu-65 (alpha, n), Ag-107 (alpha, n), Sb-12 1 (alpha, n), Sb-123 (alpha, n), Ho-165 (alpha, n), Au-197 (alpha, n), in a number of target nuclei from A = 55 to 197 (Z = 25 to 83) have b een calculated using the Statistical Model with and without inclusion of pre-equilibrium particle emission in the energy from threshold to 4 0 MeV. It is found that without consideration of pre-equilibrium decay , the data are not reproducible. As expected, inclusion of pre-equilib rium emission in compound nucleus calculation agree well with the expe rimental excitation functions. The pre-equilibrium fraction (FR) is fo und to be dependent on excitation energy, target mass number, neutron number, atomic number and, asymmetry parameter (N-Z).