  We theoretically analyzed inelastic effects in the electron transport through
molecular junctions originating from electron-vibron interactions. The
molecular bridge was simulated by a periodic chain of identical interacting
hydrogen-like atoms providing a set of energy states for the electron
tunneling. To avoid difficulties inevitably arising when advanced computational
techniques are employed to study inelastic electron transport through
multilevel bridges, we propose and develop a semiphenomenological approach. The
latter is based on the Buttiker's dephasing model within the scattering matrix
formalism. The advantage of the proposed approach is that it allows to
analytically study various inelastic effects on the conduction through
molecular junctions including multilevel bridges. Here, we apply this approach
to describe features associated with electron energy transfer to vibrational
phonons which appear in the inelastic tunneling spectra of electrons. In the
particular case of a single level bridge our results agree with those obtained
by self-consitent calculations carried out within the nonequilibrium Green's
functions method validating the usefulness of the suggested approach.
