Probing Nuclear Dissipation With Light-Ion-Induced Fission Excitation Functions

Determination of nature and strength of nuclear dissipation is a hot topic of current nuclear physics. Experimental data provided by fusion fission reaction, such as fission and evaporation residue cross section, particle multiplicity, etc., have been used to investigate nuclear dissipation properties in fission. Employing a Langevin equation coupled with a statistical decay model, we have studied the dissipation in fissioning systems that are populated by light ions.In the framework of Langevin model, the presaddle dissipation strength of (3-5) x 1021s-1 has been extracted by comparing theoretical predictions with fission excitation function data measured in p+206 Pb and p+209 Bi systems. Furthermore, we survey the roles of (initial) excitation energy and angular momentum in the sensitivity of fission cross section to presaddle friction. It has been found that high energy and low angular momentum can significantly increase the sensitivity. These findings suggest that on the experimental side, to accurately obtain information of presaddle dissipation strength through the measurement of fission excitation function, it is optimal to choose those excited nuclear systems produced by high-energy light-ion-induced spallation reactions.