Anatoly,
The point is, to my opinion, that since In the most interesting range, below 2nm, the plasmon activity decreases, therefore its effect on EXAFS interpretation, if any, should be negligible.
I think I may not understand your point. The Zhao and Montano paper shows very pronounced changes in the plasmon spectra between each of 10,3,2, and 1 nm for Al. At 1 nm, the surface plasmon is definitely dominating -- not going away. So their conclusion, that lambda changes substantially below 10 nm due to the changing relative importance of surface-to-bulk plasmons seems well-argued to me (not to say its correct). I agree (I think) with Matthew that the Zhao and Montano work shouldn't be too easily dismissed, though it might not be completely correct. I don't know of any other work on how lambda might depend on particle size, and never really thought about this. The Rao paper seems broader in scope and not necessarily addressing plasmons and mean free path, but I only skimmed it, so maybe I missed something. Their fig 8 definitely shows a size dependence of O K-edge, though I didn't immediately see a clear interpretation for this -- it could have several explanations. Again, I only skimmed this paper, so maybe I missed something: perhaps the electron diffraction literature has more information??
... There are other evidences that small particles have DOS similar to molecules, not typical metals. Most notable is the evidence that HOMO-LUMO band grows to more than 1 eV at sizes of 1 nm range.
Hmm, I'm not sure I see that becoming more molecular and less metallic indicates that using the bulk mean-free-path is OK. . The 'universal mean free path' that Feff uses and the fact that S02 is still has to be a fitting parameter even for excellent data with Feff8 suggests to me that there may be many hidden sins in Feff's mean-free-path calculation. Sadly, we seem to be a little short on theorists these days. --Matt