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Homework Help: Spectroscopy (Molecular,Microwave)

  1. Mar 23, 2013 #1
    1. The problem statement, all variables and given/known data
    The bond length of CO is 1.128 Å. At what wavenumbers do the first three rotational transitions appear

    2. Relevant equations
    μ= (m1m2/m1+m2)
    I = μr0^2
    B= h/(8∏^2)IbC
    ΔE = 2B (J+1)

    3. The attempt at a solution

    For the first equation I got

    (12 x 16) / 28 = [(6.857 /1000)/ avagadro number] = 1.138 x 10^-26

    For the second equation I got

    (1.138 x 10^-26) x (1.128 x 10^-10)^2 = 1.44 x 10^-46 kg/m^2

    For the third equation I got

    planck's constant / [(8∏^2) x (1.44 x 10^-46 ) x (speed of light)] = 1.93cm^-1

    I honestly don't know what to do after this please help
    really appreciated and thank you very much
  2. jcsd
  3. Mar 25, 2013 #2


    User Avatar

    Staff: Mentor

    You're doing fine. What about the fourth equation you listed?
  4. Mar 25, 2013 #3
    Thats the problem, I know the answer is in that equation but I just do not know how to use it to get the values for the first 3 rotational energy levels. Just don't know to tackle that equation.Thanx for the reply
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