Probability of nuclear fission by intermediate energy particles

In the cascade-evaporation model of nuclear reactions and liquid-drop model of fission the experimental dependence of fissionability on the target nucleus mass for stopped π- mesons and γ quanta, protons and α particles with energies less than 1 GeV is analyzed. The effect of the shell effects, pre-equilibrium emission by the excited nuclei, uncertainty of the liquid-drop-model parameters and dependence of the fission barrier on the excitation energy of the nucleus on fissionability is investigated. In the incident particle energy range 600-1000 MeV the thermal effects can produce a great influence on the fission probability. The most sensitive nucleus characteristics is the fission barrier, which value for average nuclei can noticeably decrease at high excitation energies. The cascade-evaporation model can describe by a unified way the probability of nuclei fission by γ quanta, π- mesons, protons and α particles of average energy. For more detailed investigation of nuclei fission it is necessary to improve the modern model formulation first of all including the correct description of the process of establishment of statistical equilibrium in the residual nucleus and the effect of the shell effects on the density of the compound nucleus levels