Electron System Thermodynamics: Plasmon Energies 5-30eV

[mcodesmart]

I need an explantion of the following description of plasmon,

"Plasmon energies in the range of 5-30eV for electron systems of metallic densities,consequently they play no role in determining the thermodynamic properties of the electron system."

What kind of thermodynamic properties are being referred to here? What are the thermodynamic properties of an electron system? Is this like the electron free energy?

 

[Cthugha]

Things like heat capacity are thermodynamic properties.

Basically all the author wants to say is:
The typical thermal energy at room temperature is 25 meV. The plasmon energy is somewhere between 5 and 30 eV. That is a factor of at least 200 in between, making it very unlikely that plasmons are excited thermally. Therefore they will also not contribute to thermodynamic properties like heat capacity.