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2nd Order Perturbation Coefficients.

  1. Nov 12, 2013 #1
    I have found an expression for the estimated energy contribution a term |I> will bring to a wavefunction |K>

    [itex]\Delta E = \frac{|\langle I|\hat{H}| K\rangle|^2}{(E_K - \langle I |\hat{H}| I\rangle)}[/itex]

    Is there a simple way to extract the coefficient that will be associated with |I>? Even a link to relevant literature would be appreciated.

  2. jcsd
  3. Nov 12, 2013 #2


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    The first order correction to the wavefunction k reads something like
    ##|k\rangle_1=|k\rangle+\sum_I\frac{\langle I|H| k\rangle}{E_k-\langle I|H|I \rangle } |I\rangle ##
    using your notation. It is enough to calculate the second order correction to energy.
    Is it that what you are looking for?
    Any book on QM will contain a chapter on perturbation theory.
    Also wikipedi contains quite a lot:
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