Nonequilibrium emission of neutrons from fusion-like reactions of 152-MeV 16O with 154Sm

Neutron time-of-flight spectra and angular correlations were obtained in coincidence with γ rays characteristic of the xn (x = 8,9,10) and αxn (x = 7,8) fusion-like products in reactions of 151.9 MeV 16O with 154Sm. The spectra at all angles (200, 700, 1000, 1510) clearly indicate the presence of nonequilibrium neutron emission. The energy spectra can be represented in terms of isotropic emission in the rest frames of two moving sources. The slower of these moves with the speed of the center of mass; its emission corresponds to a temperature of approx.1.7 MeV. The faster source, characterized by a temperature of 5 to 6 MeV, has a velocity of approx.0.4 of that corresponding to the projectile energy above the Coulomb barrier. The yield of fast neutrons as a function of the exit channel is found to be in good agreement with the predictions of an extended incomplete fusion model. Comparisons are made with other models that lead to emission of fast neutrons