  We have applied a double decoupled localized level Anderson-Newns Hamiltonian
to the analysis of surface effects upon the ionized fraction $\mathcal{R}_{+}$
of sputtered atoms from a metal surface. Electronic excitations, induced in the
conduction band by the transient formation of quasi molecular systems, between
substrate and emitted atoms, in the collision cascade generated by the primary
incident beam, have been explicitly included into an instantaneous transition
matrix peaked at the Fermi level of the material. The interaction dynamics seem
to take place over two different time scales, one related to sputtered atom
trajectories and the other to recoiled substrate particles. Finite temperature
calculations have suggested, at very low ejection energies, a power law
dependence of the final charge state of the sputtered beam on its detected
velocity. This result is in agreement, in the zero temperature limit, with some
previously published papers and its validity has been compared to other
theoretical outcomes and tested on SIMS data.
