Why Does an Electron Release a Photon After Absorption?

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Discussion Overview

The discussion revolves around the phenomenon of an electron releasing a photon after absorbing one, exploring the underlying reasons for this behavior. It touches on concepts from quantum mechanics, including spontaneous emission, energy states, and probabilistic interpretations of particle behavior.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant describes the process of an electron absorbing a photon and moving to a higher energy state, questioning why it subsequently releases a photon and returns to the ground state.
  • Another participant identifies the phenomenon as spontaneous emission, suggesting that quantizing the electromagnetic field provides insight into the process.
  • A different viewpoint suggests that the electron's return to the ground state is influenced by statistical probabilities, positing that there is a greater likelihood of occupying lower energy states over time.
  • One participant reflects on a similar question raised in an academic setting, attributing the emission of the photon to the inherent probabilistic nature of quantum mechanics and the average time until emission occurs.
  • Another participant notes that excited states are not eigenstates of the full hydrogen plus electromagnetic field Hamiltonian, leading to a mixture of states that includes a nonzero projection onto the ground state.

Areas of Agreement / Disagreement

Participants express various interpretations of why an electron releases a photon, with no consensus reached on a singular explanation. Multiple competing views regarding the mechanisms and probabilities involved remain present in the discussion.

Contextual Notes

The discussion includes assumptions about quantum mechanics and the nature of energy states, which may not be fully articulated. The relationship between statistical probabilities and the behavior of electrons in excited states is also a point of contention.

Timothy Schablin
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After an electron absorbs a photon, it will move to a higher energy state. It then releases a photon and returns to its ground state. But why does the electron release the photon? Why does it not remain in that energy state? What forces it to return to ground state?
 
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What you describe is spontaneous emission. You get it by quantizing the electromagnetic field.
 
Timothy Schablin said:
What forces it to return to ground state?
One way to look at it is that there is a much greater probability of it ending up in the lower energy (unoccupied) state than in the higher state. Like if you build a pyramid of balls and you leave one out of a lower space. They may stay there for a while but they will eventually settle and only the lower energy states are occupied.
Statistics appears to create 'Forces" in many situations.
 
Hah, I remember asking exactly the same question during our "material science" lecture in my EE Master's. Sadly, it was back then met with obvious ignorance from the lecturer.

To my understanding, the answer lies in the inherent probabilistic nature of quantum mechanics. The probability of emitting the photon is higher to emit than not; so, it's a question of "average time" until it will do so.
 
The excited states are not eigenstates of the full hydrogen+EM field hamiltonian and thus will evolve into a mixture of other states, with in general a nonzero projection onto the hydrogen ground state.
 

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