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No vibration spectrum for homonuclear diatomic molecules?

  1. Jul 2, 2015 #1
    Supposed to be because they have a zero dipole moment...

    Dipole moment is variously described using neutral systems of pairs of opposite charge, or single items with charge, but I am finding no explanations of same charge pairs I understand..

    Wiki states: "To show a vibrational spectrum, a diatomic molecule must have a dipole moment that varies with extension. So, homonuclear diatomic molecules do not undergo electric-dipole vibrational transitions. So, a homonuclear diatomic molecule doesn't show purely vibrational spectra."

    How does the dipole moment not vary with extension?
  2. jcsd
  3. Jul 2, 2015 #2


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    In a homonuclear diatomic molecule there is no dipole moment because of the additional symmetry. Therefore, the dipole moment is zero regardless of extension and thus independent of the extension.
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