Fusion probability of massive nuclei in reactions leading to heavy composite nuclear systems

Reactions between massive nuclei show a considerable reduction in fusion-evaporation crosssections at the Coulomb barrier according to the comparison of experimental values with those calculated by barrier passing (BP) and statistical model (SM) approximations. Reduced fusion cross-sections corresponding to fusion probability P-CN<1 are accompanied by a high probability of deep -inelastic and quasi-fission processes arising on the way to fusion. At the same time, the excitation functions for evaporation residues (ERs) obtained in very mass-asymmetric projectile-target combinations are well described in the framework of the BP model (assuming P-CN=1) and SM approximations. In the framework of SM, the survivability of produced heavy nuclei can be described with the use of adjusted macroscopic fission barriers. Fusion suppression appears in less asymmetric combinations, for which P-CN values can be estimated using survivability obtained for very asymmetric ones leading to the same CN. An attempt was made to systemize the P-CN data derived from different projectile-target combinations leading to ERs in the range from Pb to the most heavies, which are compared with P-CN values obtained in fission experiments.