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Calculating the frequency of the fundamental vibrational mode

  1. Jul 17, 2012 #1
    Can you calculate the frequency at which a bond vibrates when you know what frequencies of EM radiation it absorbs? Using carbon monoxide as an example. It has a stretching frequency at around 2100 cm-1. In electron volts, that would be around 0.3 eV. If I'm not mistaken, this is the energy it absorbs to jump from n=0 to n=1 (or is it n=1 to n=2?). Anyhow, if its the former then ΔE = [itex]\frac{3}{2} - \frac{1}{2}hf[/itex] = hf.

    I know that the equation to calculate the energy of vibrational normal modes is [itex]E_n=hf(n + \frac{1}{2})[/itex] so wouldn't that mean that the energy of the n=0 mode is equal to [itex] \frac{0.3 eV}{2}[/itex]?
  2. jcsd
  3. Jul 18, 2012 #2

    Simon Bridge

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    That's certainly what it means.
    The classical picture is that this is the frequency of the fundamental at which the two atoms vibrate towards each other.
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