Effects of Isospin on Pre-scission Particle Multiplicity of Heavy Systems and Its Excitation Energy Dependence

Isospin effects on particle emission of fissioning isobaric sources ²⁰²Fr, ²⁰²Po, ²⁰²Tl and isotopic sources ^189,202,212Po, and its dependence on the excitation energy are studied via Smoluchowski equations. It is shown that with increasing theisospin of fissioning systems, charged-particle emission is notsensitive to the strength of nuclear dissipation. In addition, wehave found that increasing the excitation energy not onlyincreases the influence of nuclear dissipation on particleemission but also greatly enhances the sensitivity of the emissionof pre-scission neutrons or charged particles to the isospin ofthe system. Therefore, in order to extract dissipation strengthmore accurately by taking light particle multiplicities it isimportant to choose both a highly excited compound nucleus and aproper kind of particles for systems with different isospins.