Neutron emission from products of strongly damped reactions 58Ni+165Ho at 930 MeV.

Abstract

Neutron time-of-flight spectra have been measured for emission from products of reactions between {sup 58}Ni and {sup 165}Ho at a bombarding energy of 930 MeV. Neutrons were detected in coincidence with projectilelike fragments from strongly damped reactions using a heavy ion {Delta}{ital E}-{ital E} telescope which permitted the total kinetic energy loss to be extracted for each event. The neutron spectra were separated into 25-MeV-wide total kinetic energy loss bins over the total kinetic energy loss range from 0 to 450 MeV. Moving source fits were made to the neutron spectra to determine emission temperatures, multiplicities, velocities, and angles for the projectilelike fragment, targetlike fragment, and nonequilibrium emission sources as a function of the total kinetic energy loss. The extracted temperature of the projectlike fragment is found to be larger than that of the targetlike fragment source at all total kinetic energy losses, approaching that of the targetlike fragment only at the largest total kinetic energy losses. The results suggest an equal division of the available excitation energy at small total kinetic energy loss with a thermal energy division occurring only at the largest total kinetic energy losses. The velocity of the nonequilibrium source is found to remain constant atmore » approximately one-half of the beam velocity independent of the final projectlike fragment velocity. This result supports models of nonequilibrium emission in which nucleon emission is isotropic in the nucleon-nucleon center-of-mass system as opposed to models in which the nonequilibrium emission occurs isotropically from the heavy fragments along their reaction trajectories.« less