In quantum mechanics electron in an atom is described by the wave function of probability. When the electron changes level the wave function changes to another. Is the changing electron level when it emits or absorbs photons have any time duration or it happens immediately?

  • $\begingroup$ Is this a question for the lifetime of an electron in a certain energy level? Or is the question if the process of changing (jumping) between two Quantum mechanical states takes some time? $\endgroup$ Aug 15, 2021 at 19:31
  • $\begingroup$ Have a look at this paper arxiv.org/pdf/1803.00545.pdf. The authors find that a short time before the jump occurs there are warning signs that can be used to predict the jump and to reverse it. This short time could be interpreted in some way as the duration of the jump $\endgroup$
    – Prallax
    Aug 15, 2021 at 19:31
  • $\begingroup$ Not exactly what you asked, but the photoelectric effect (where the electron is ejected from the material) takes a finite time and this time has been measured experimentally. I believe the same must be true for transitions within the atom, but I have no sources for that. $\endgroup$ Aug 15, 2021 at 19:33
  • $\begingroup$ This question is about the process of changing the electron energy level to another in an atom. Does the jumping have some time? $\endgroup$
    – Lexorde
    Aug 15, 2021 at 19:41

1 Answer 1


By the uncertainty relation $\Delta E*\Delta t\approx h$ there must be time otherwise $\Delta E$ would be very large.

  • $\begingroup$ The uncertainty on the energy of the jump is correlated in this way to the half-life of the excited state (short lived excited states have broader emission lines), not to the time it takes to do the actual jump. $\endgroup$
    – Prallax
    Aug 15, 2021 at 20:34
  • 1
    $\begingroup$ But $\Delta t$ here is the lifetime of the excited state, $\Delta E$ the corresponding width of the line (natural line width). This is not what the question asked for... $\endgroup$ Aug 15, 2021 at 20:34

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