Limitations to presaddle neutron emission from fission-fragment charge distributions.

The e8'ect of including mass-asymmetry dependent 6ssion delay times into the statistical model has been investigated. The shape of the predicted charge distribution of fission fragments is found to be very sensitive to the magnitude and mass-asymmetry dependence of these delay times. Measured mass-asymmetry dependent prefission neutron multiplicities were fit with calculated presaddle values by varying the 6ssion delay times. The resultant predictions for the charge distributions are found to have shapes inconsistent with those measured for similar mass systems, indicating that measured prefission multiplicities cannot be accounted for by presaddle emission alone. Limitations to the magnitude of the presaddle component are discussed.