  A semimicroscopical approach is formulated to describe the direct nucleon
decay of various giant resonances in intermediate and heavy mass spherical
nuclei. The approach consists in: (i) the exact continuum-RPA calculations for
amplitudes of the reactions accompanied by excitation and the nucleon decay of
the collective particle-hole states (doorway states); (ii) the Breit-Wigner
parametrization of the RPA reaction-amplitudes in the vicinity of the giant
giant-resonance energy and evaluation of the doorway-state parameter (the
energy, entrance and partial nucleon, escape widths); (iii) the
phenomenological consideration for the doorway-state coupling to many-particle
configurations with the use of reasonable statistical assumptions and
derivation on this base the expressions for the energy-averaged reaction
amplitudes. The nuclear mean field and quasiparticle interaction are the input
quantities for calculations. Examples of description for the direct nucleon
decay of a number of giant resonances in the $^{208}Pb$ parent nucleus are
given together with the comparison with corresponding experimental data.
