We study in the framework of the Langevin model the influence of initial excitation energy(E*) of Hg compound nuclei(CNs) on the sensitivity of the excitation energy at scission(Esc*) to the nuclear friction strength(β).It is shown that the sensitivity is enhanced substantially with increasing E*.Moreover,we find that the significant sensitivity of Esc* to β at high E*is little affected by a marked difference in the neutron-to-proton ratio of a CN and in its size and fissility.Our findings suggest that,on the experimental side,a measurement of Esc* in energetic proton-induced spallation reactions can provide not only a sensitive but also a robust probe of nuclear dissipation in fission of highly excited nuclei.Further development of a suitable approach to spallation reaction is discussed.
The stochastic Langevin approach to fission is applied to analyze fission excitation functions measured in p+~206Pb and p+~209Bi systems. A presaddle friction strength of(3–5)×10^(21)s^(-1)is extracted by comparing theoretical predictions with experimental data. Furthermore, the small distortion of the formed compound nuclei with respect to the spherical shape under the condition of low angular momentum suggests that experimentally, populating an excited compound system via light-ion induced reactions favors a more accurate determination of presaddle friction with a fission cross section.
