The quasistatic approach

to describe the motion of the substrate on a physical time scale, an equation of motion needs to be solved that inevitably involves the substrate ma.ss. However, there are no physical criteria on which the choice of a specific value for this mass could be based. Second, even though the substrate is a macroscopic object in the SFA experiment, its mass cannot be too mucli larger than the mass of a film molecule in the NEMD simulations because otherwise the wall would remain at rest on the time scale on which film molecules move. In fact, the ratio of the mass of a single film molecule to that of the entire wall is sometimes as small a.s i/8 [191, 192] so that one can expect relaxation phenomena in the film to depend sensibly (and therefore unphysically from an experimental perspective) on this arbitrarily selected wall mass [170]. Third, the speed at which the walls are slid in the SFA experiment is typically of the order of 10 — 10 Aps [136] so that under realistic conditions the walls remain practically stationary on a typical length and time scale of molecular relaxation processes. 

---

Here results are obtained in the discrete dipole approximation, so they should give the exact solution to the electromagnetic problem and spectra identical to the Mie theory. An3way, like already shown in literature [1], the quasistatic approach is able to retain the most important features in the spectra for spheres of these sizes. 

---