# Statistic mechanics - particles with energy 0

captainjack2000

## Homework Statement

System of weakly interacting particles in equilibrium temperature T, each particle can exist in three energy states -epsilon, +epsilon and 0. There are three times as many particles in the -epsilon state as in the +epsilon state. Show that fraction of particles with energy 0 is sqrt(3)/(4+sqrt(3)) ?

## Answers and Replies

Staff Emeritus
Homework Helper

There's an equation that gives the relative probability, or number, of particles occupying different energy states. Should be in your textbook or class notes ... it contains the number e, as well as T and k.

latentcorpse

is it along the lines of P(E_i)=e^{-E_i/kT}/(sum_j e^{-E_j/kT})

thats probably wrong but could you confirm please...

Staff Emeritus
Homework Helper

Yes, that's the one.

aurora14421

I'm stuck on the same question. I have the expression for the probabilities but I can't get the final expression they have. Any chance of another hint? I've been staring at this for a while and getting nowhere.

Staff Emeritus
Homework Helper

P(E_i)=e^{-E_i/kT}/(sum_j e^{-E_j/kT})

Use this ↑ equation to write an expression for the ratio:

P(E=-ε) / P(E=+ε)

Welshy

Use this ↑ equation to write an expression for the ratio:

P(E=-ε) / P(E=+ε)
Was stuck at this too! I get it now. Thanks!

aurora14421

Yeah, thanks for the help. I got it too.