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Homework Help: Spring constant of molecule

  1. Oct 16, 2007 #1
    I have to determine the spring constant for a diatomic molecule. I have the frequency in cm^-1 which is 1395.
    I know the relation between the angular frequency and spring constant so I use the following relation:
    omega = 2*pi*c*v = sqrt(k/mu)

    so I isolate for k = mu*(2*pi*c*v)^2

    mu = 8*1.66*10^-27
    v = 1395 cm^-1

    which gives me k = 9.18*10^-6 kg/s^2

    This strikes me as a rather strange result? For a diatomic molecule I would expect something like at least 400-800 N/m for the bond force? What is wrong ? Thanks in advance.
  2. jcsd
  3. Oct 17, 2007 #2


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    I'm not sure how exactly you go from frequency to wavenumber (or viceversa). It looks like you've used a linear dispersion with some value of c. What value did you use? Where did you get this from? Experimentally, how is the frequency measured (and why is the output in the form of a wavenumber)?
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