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What happens during a change in orbital state?

  1. Nov 21, 2008 #1
    Consider a hydrogen atom with an electron in some excited state. Now, in order for an electron to drop to a lower state, a photon of a specified energy, which is determined by the energy difference of the two states, must be emitted.

    Do we know what happens to the electron during this transition? Does the electron physically move to the lower state in a manner that is possibly governed by the laws of relativity? Or, does the electron at the higher energy state cease to exist and a "new" electron comes into existence at the lower energy state in a manner that might be instantaneous? Also, does the emitted photon have a preferential direction, and if so, what determines it?
  2. jcsd
  3. Nov 21, 2008 #2
    I can't say what actually happens however the electron certainly changes states in a classical way, it must move over space in order to produce a photon, since that is the definition of the photon. It would not be light if it was just two static points of EM.

    When an electron moves from one point to another it creates half of the complete occilation of an electromagnetic wave, which would be your photon.

    The highest strength of the electromagnetic wave's propogation (the direction the light woul d be emited) would be perpendicular to the movement of the electron, it would not emit any light in the direction it is moving.
  4. Nov 21, 2008 #3


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    Staff: Mentor

    First, the very notion of the electron "moving" from one position (x,y,z) to another in a classical-like trajectory is questionable in QM. This notion exists only in some interpretations of QM, e.g. the Bohmian interpretation. Even in the Bohmian interpretation the trajectories are rather weird by classical standards.

    Second, the probability distributions for the initial and final states overlap in position to some extent, so there is no need for the electron to "move" in that way during the transition. Don't think in terms of well-defined circular or elliptical orbits as in the Bohr-Sommerfeld model which has been obsolete for about eighty years! The expectation value of the position (i.e. the average value of the position for the entire wave function) is different before and after, but that's another matter.
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