LIGHT-PARTICLE EVAPORATION AS A FUNCTION OF NEUTRON EXCESS FOR MEDIUM-MASS COMPOUND NUCLEI WITH E(X)APPROXIMATE-TO-2 MEV/U

Light-particle emission from the fission reactions of Cu-63+Mo-92,Mo-100 and Ne-20+ Sm-144,Sm-148,Sm-154 has been studied using the Texas A&M Neutron Ball detector. Linear-momentum transfers (LMT) were determined from fission-fragment-folding-angle measurements. An increase of neutron multiplicity with apparent linear-momentum transfer was seen. The initial excitation energies of the compound nuclei are estimated from the observed linear-momentum transfer and also reconstructed from the measured multiplicities and average energies of neutrons, protons and alpha-particles. The results of the two methods are in good agreement. The observed neutron multiplicities show a strong increase with increasing neutron-to-proton ratio of the composite system. The light-particle multiplicities are compared with calculated values using the statistical code GEMINI. The effect of the dynamic fission delay on the total light-particle multiplicities is explored and found to be small.