The reliability of realistic M3Y effective NN interactions to describe mult
istep direct (MSD) processes is proved by analyzing the corresponding real
optical potentials. This trial is done in order to overcome the uncertainti
es of the effective NN-interaction strength V-0 obtained by direct fit to t
he experimental data. The microscopic potential for the nucleon-nucleus sca
ttering at energies lower than 50 MeV has been calculated by using nucleoni
c and mesonic form factors. It has been analyzed through (i) a comparison w
ith phenomenological optical potentials, and (ii) its use for description o
f nucleon elastic-scattering angular distributions. It results that the str
ongly simplified model interactions usually involved within MSD reaction th
eory, e.g. 1 fm range Yukawa (1Y) term, neglect important dynamical details
of such processes. An 1Y-equivalent V-0 strength of a realistic effective
NN interaction is determined by corresponding optical-potential volume inte
grals, and involved within Feshbach-Kennan-Koonin theory calculations. (C)
2001 Elsevier Science B.V. All rights reserved.