The evaporation residue cross sections oER in reactions between massive nuclei have been analyzed within di8'erent models of complete fusion. The calculations in the framework of the optical model, the surface friction model, and the macroscopic dynamic model can give the results which are by few orders of magnitude different from experimental data. This takes place due to neglect of the competition between complete fusion and quasifission. A possible mechanism of compound nucleus formation in heavy-ion-induced reactions has been suggested. The analysis of the complete fusion of nuclei on the basis of dinuclear system approach has allowed one to reveal an important feature of the fusion process of massive nuclei, that is, the appearance of the fusion barrier during dinuclear system evolution to a compound nucleus. As a result, the competition between complete fusion and quasifission arises and strongly reduces the cross section of the compound nucleus formation. A model is proposed for calculation of this competition in a massive symmetric dinuclear system. This model is applied for collision energies above the Coulomb barrier. The crER values calculated in the framework of dinuclear system approach seem to be close to the experimental data. For illustration the reactions Mo+ Mo, Pd+ Pd, and Sn+ Zr have been considered. PACS number(s): 25.70.Gh, 25.70. Jj, 24.10.i

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The dynamical effects of the entrance channel on the formation of the evaporation residues are studied by analyzing the 40 Ar + 176 Hf, 86 Kr + 130,136 Xe, 124 Sn + 92 Zr, and 48 Ca + 174 Yb reactions leading to the 216 Th * and 222 Th * compound nuclei. We find that the difference between the evaporation residue cross sections for the reactions leading to the same compound nucleus is caused by the different angular momentum distributions of the partial fusion cross sections σ fus (E c.m. ). The strong dependence of the fusion angular momentum distribution on the mass (charge) asymmetry and shell structure of reactants is demonstrated. The effect of the A/Z ratio for the 86 Kr + 130,136 Xe reactions is discussed. The dynamical conditions of capture affect the competition between complete fusion and quasifission and, consequently, the shape of the angular momentum distribution of the compound nucleus. By this way the peculiarities of the entrance channel also affect the fission-evaporation competition of the excited intermediate nuclei along the deexcitation cascade of the compound nucleus and, consequently, the evaporation residue formation.

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