Talk:Plasmon

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In the second paragraph: "... because the electrons in the metal screen the electric field of the light." that doesn't seem to make any grammatical sense, but I may be wrong.

• Read "screen" as a verb not a noun. ie. the electrons (which are in the metal) are screening the electric field.

[edit] More screening woes

I still don't understand this use of the word 'screen' even as a verb. As I understand it to screen means 'to examine', 'to block'* or 'to display' none of which fits the context as far as my understanding of this subject goes.

Either I'm being incredibly ignorent or in this particular situation 'screen' is a colloquial term or jargon.

• If this is the case, 'screen' is not a particularly informative word when related to the physical processes actually taking place.

What is meant is 'screening' as in 'blocking' the electric field. See Electric field screening. I think the description is accurate, but I'm not quite sure. I'll check some refrences over the week-end. O. Prytz 22:53, 6 January 2006 (UTC)

I am more worried about the correctness of the physics. First, shouldn't the plasma frequency of copper be in the ultraviolet as well? Second, I always thought that the colors of metals are mostly due to the positions of their "interband transition" thresholds. Gold is yellow because blue light can cause electronic transitions from the occupied states in the "d band" to the unoccupied states in the "s band", and is therefore strongly absorbed. The same goes for copper, I suppose. See Electronic band structure. Finally, what geometrical factors exactly affect the plasma frequancy of gold? Just asking...

[edit] plasma frequency for some materials

I agree, the plasma frequency should be in the UV also for copper, see e.g. . But the matter seems to be quite complex, especially in the noble metals. The characteristic colour of copper and gold should be attributed to electronic transitions from d-bands to the conduction band. The energy of these transitions are in the blue region, thus both metals appear reddish and yellowish, respectively.

One more remark: The plasmon frequency for semiconductors is usually in the very deep UV, not IR! Around 15-16 eV. That's why they look silverish - like metals. You cannot use the standard free-electron-gas model to calculate the plasma frequency (this is, what gives IR-frequencies). As I haven't digged deep enough into the matter, I won't change the article. But if there is someone more experienced around, please do it! (With some references...) That would be great!