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1st order pertubation on 2 level system

  1. Nov 27, 2011 #1
    Hi all. I m stucked on the question followed, any helps will be greatly appreciated.

    A perturbation has the form H'=z act on a two level system which they have different parity.

    So the first order correction to the energy level 1 and 2 are give by:

    E11=<ψ1| H'1>

    Same for level 2.

    These two energy correction are clearly zero because the same level has same parity.

    However the first order wavefunction corrections are not for both level:

    According to time independent non-degenerate perturbation theory on the 1st order correction to the wave function formula:

    ψ11=<ψ2| H ' | ψ1>/(E1-E2) ψ2

    Which is none zero

    Where am I wrong? I am so confused..thanks in advance.
  2. jcsd
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