The multiplicities of prescission protons and α particles in the reaction ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$${+}^{232}$Th at 104, 110, 116, and 118 MeV have been measured. The observed multiplicities are much larger than the prediction of the statistical model without the introduction of fission delay. An analysis of the prescission proton and α data along with that for neutrons (measured earlier) has been made using deformed optical model and deformation-dependent particle binding energies. Simultaneous fits to the charged particle and neutron data required a total fission time scale in the range of (25–80)× ${10}^{\mathrm{-}21}$ s. For this system, the mean kinetic energies of the prescission particles are insensitive to the division of the total delay time into presaddle and postsaddle components; however, the neutron and charged particle multiplicity data are sensitive to the deformation of the saddle-to-scission emitter. The analysis shows that postsaddle emission takes place close to the scission point.

• Received 2 June 1995

DOI:https://doi.org/10.1103/PhysRevC.52.3167