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Homework Help: So confused another stupid question

  1. Sep 25, 2006 #1
    I've read the chapter but it hasn't helped. Eigenstates are states with a definite amount of energy independent on time? and then any other state is a linear combination of the eigenstates, with some Cn acting as a weighting factor...is there a limitation on what the Cn's can be? otherwise, wouldn't non-stationary states be unquantized?
  2. jcsd
  3. Sep 25, 2006 #2
    In fact, the [itex]|c_n|^2 [/itex] are the probabilities of measuring the energy value [itex]E_n[/itex]. Remember that quantum mechanics assumes that the wave function collapses to an energy-eigenstate when the energy is measured, so the measured energy is still quantized.

    This "collapse" means the wavefunction is

    [itex] \Psi = \sum \limits _n c_n \varphi_n[/itex] before the energy is measured, where the [itex] |c_n|^2 [/itex] say how probable it is to measure energy [itex] E_n [/itex].

    Right after the measurement of energy [itex] E_n [/itex], the wavefunction collapses to

    [itex] \Psi = \varphi_n [/itex].
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