# Plasma Frequency

1. Mar 25, 2007

### luke

Does anyone know where I can find measured values for the plasma frequency of bulk silver? I would like them to be for light in the Terahertz range. I have looked in all type of book of optical constants and I have searched many different articles. Just a suggestion of where to look would be nice. Thanks

2. Mar 25, 2007

### Dr Transport

do a google search under silver plasma frequency......

3. Mar 26, 2007

### luke

Yeah I have searched google. My only problem is that I have seen values that range from 1300 THz to 24 THz. To just have a value that is within an order of magnitude would be good. Thanks for the reply

4. Mar 26, 2007

### luke

thank you for your help since the suggestion to do a google search lead me to an article which states "For bulk silver a value of 1 / τ = 2.4 × 10^13 s− 1, is the common text book value used to fit the plasmons resonance near 400 nm." Well this reminded me that the plasma frequency depends on the wavelength but for what I am doing I do not need the plasma frequency for any wavelength I just need it for a single wavelength. So I think this problem is solved since I was searching for something I didn't need.

Thanks again

5. Oct 24, 2007

### Marcie

plasma frequency of silver

The plasma frequency of silver is 2.17 *10^15 Hz or 138 nm. This is calculated from the equation plasma frequency = sqrt(4*pi*N*e^2/m_0), where N is the number of electrons per cm^3, e = 4.8E-10 esu, m_0 is the electron mass m_o=9.11E-28 grams. The plasma frequency will be in Hertz or 1/sec.

Tau is the momentum scattering time. A good explanation is in Mark Fox's book "Optical Properties of Solids".

6. Oct 24, 2007

### GreatMinds

Brilliant! A simple yet effective way to find the answer to everything!

7. Mar 28, 2008

### quantasham

Plasma frequency for silver : 3.75(eV)-3.80(eV)

reference:
1. Phys. Rev. 132, 1599 - 1602 (1963)
2. Phys. Rev. Lett. 5, 470 - 472 (1960)

I try to use the formula suggested by Marcie, using n=5.86*10^22 (cm^-3) (from the book by Ashcroft) and I get 8.99(eV).

Well, I hope someone can tell me why the formula doesn't work. I found an article saying that there is a reflection minimum at 9.2(eV). See :Phys. Rev. 121, 1100 - 1103 (1961). I am not sure if the 9.2 eV has anything to do with the calculated 8.99eV.

8. Sep 22, 2008

### itamblyn

The equation in Ashcroft & Mermin is for the case of a free electron gas in the presence of a uniform positive background (i.e. the jellium model). It is only an approximation of the real system, so it will never give you the "correct" answer. It does a pretty good job though, especially for simple metals at STP.

9. Jan 28, 2009

### affablelochan

for quantasham,
For pure SIlver it will be the value you calculated. But for doped Silver which is a semiconductor its value is nearly 9 ev.

I need plasma frequency for all the doped semiconductor for my research. My question is
1) Is there a range for maximum and minimum doping of a semiconductor?
2) Plasma fy= sqrt(4piNe^2/m0); Is N the doping concentration in case of doped semiconductor?
3) how to convert frequency in Hertz to ev?

10. Sep 28, 2010

### zidanetribal2

Thank you for wasting my time. My unrelated google search for 'Plasma frequency of silver' has this discussion as the first hit. Your useless reply has contributed in destroying the internet. Good job.