# Surface plasmons and hot electrons

1. Nov 27, 2013

### prehisto

Hello,Im reading a article about water spliting device in which all necessary charge carriers for water spliting arise from surface plasmons.

This is the article:
http://www.nature.com/nnano/journal/v8/n4/full/nnano.2013.18.html#f1

So i do not understand how charge carriers arise form surface plasmons.
Could someone help me with this?
Meiby give me some kind a link where surface plasmons and hot electrons are explained.So far I havent found any article which gives qualitative explanation of surface plasmons and charge carries.

2. Nov 27, 2013

### DrDu

They write that the plasmons decay into electron-hole pairs.
This happens also for bulk plasmons, when their wavenumber is large enough.
See e.g. Fig. 5.5 in the following document:
http://www.lptl.jussieu.fr/files/chap_eg(1).pdf

3. Nov 27, 2013

### prehisto

Thanks for the reference to decay.
Im sorry,but i cant make sense of fig.5.5

4. Nov 28, 2013

### DrDu

The gray shaded area is the region where particle hole excitations are possible.
Where the line $\omega_p$ lies inside this region, the plasmon can decay rapidly into particle hole pairs. Thats also what happens in the gold nanorods you are interested in.
Basically, the nanorod acts as a gigant antenna whose resonance frequency is determined by the surface plasmon resonance, but the oscillation of the charges is strongly damped as they decay into electron hole pairs. These separate and wander into the platinum grains or cobaltum oxide where they reduce/ oxidize water.

5. Dec 1, 2013

### prehisto

I m sorry but I have further questions about the graphic.
What is ω_(-) and what is ω_(+)? Are they just notation for graphical boundaries?
And K_F stands for wave number?

6. Dec 1, 2013

### DrDu

k_F is the Fermi wavenumber, i.e the maximal wavenumber electrons in have in a Fermi gas at zero temperature.
The two omegas are simply the limits above/below which electron-hole pairs exist.

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