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The Boltzmann distribution of uniformly spaced energy levels

  1. Feb 25, 2008 #1
    The question states:
    A system has energy levels uniformly spaced at 3.2x10^-10 J apart. Thepopulations of the energy levels are given by the Boltzmann distribution. What fraction of particles is in the ground state at T=300K.

    I know that the Boltzmann distribution is:
    [tex]_{}p*[/tex]j=probability that a particle is in state j
    =exp(-[tex]_{}E[/tex]j/KT) / [tex]\sum[/tex]exp(-[tex]_{}E[/tex]j/KT)

    I created my own expression for the energy state Ej:
    [tex]_{}E[/tex]j=3.2x10^-20(j-1)
    My thought process behind this was that to get the energy state of each level you have to multiply by the space between each level times 1 minus the level. In other words, E1=0*3.2x10^-20, E2=1(3.2x10^-10)...etc.

    I set this pj* equal to: # particles in ground state (g) / # states (t)
    Assuming that the particles in the ground state would have energy E=0 I plugged all of the given values into the equation: T=300, Ej=0, K=boltzmann's constant. Because the problem did not give the number of states my answer is in terms of t. I got an answer of:
    -0.25875/(1+t)
    Obviously this is wrong because you cannot have a negative number of particles.


    ANY IDEA WHAT I'VE DONE WRONG??!?!?
    thanks in advance for any help
     
    Last edited: Feb 25, 2008
  2. jcsd
  3. Feb 25, 2008 #2

    Mapes

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    Your Boltzmann distribution function has a couple of minus signs missing.
     
  4. Feb 25, 2008 #3
    I'm sorry, you are correct. The post has been edited. It was a typo, but the answer I got still stands.
     
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