  The dependence of fusion cross section on the isotopic composition of
colliding nuclei is analysed within the dinuclear system concept for compound
nucleus formation. Probabilities of fusion and surviving probabilities,
ingredients of the evaporation residue cross sections, depend decisively on the
neutron numbers of the dinuclear system. Evaporation residue cross sections for
the production of actinides and superheavy nuclei, listed in table form, are
discussed and compared with existing experimental data. Neutron-rich
radioactive projectiles are shown to lead to similar fusion cross sections as
stable projectiles.
