Neutron emission in deep-inelastic collisions induced byKr86onEr166at 5.7, 7.0, and 7.9 MeV/nucleon

Neutron emission associated with deep-inelastic collisions of 496-, 602-, and 675-MeV ${}_{}{}^{86}{}_{}{}^{}\mathrm{Kr}$ with ${}_{}{}^{166}{}_{}{}^{}\mathrm{Er}$ has been studied as a function of kinetic energy loss, fragment mass, and neutron scattering angles. The major de-excitation process is neutron evaporation from fully accelerated fragments. The excitation energy is shared between the fragments in proportion to their mass, indicating energy equilibration in the intermediate dinuclear composite system for the completely damped as for the quasielastic components. Within limits imposed by the systematic uncertainties, the angular and velocity distributions of the neutrons in the laboratory frame are consistent with isotropic emission of neutrons in the c.m. frame of the fragments. We find no evidence for pre-equilibrium effects. The observed multiplicities and energy spectra of the neutrons are consistent with predictions of statistical-model calculations.