How does an emission take place by radiation?

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    Emission Radiation
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Discussion Overview

The discussion revolves around the mechanisms of emission by radiation in semiconductors, particularly focusing on the processes involved when electromagnetic waves interact with excited electrons. It explores theoretical models and the sequence of absorption and emission events.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests that when an electromagnetic wave interacts with a semiconductor, the perturbed Hamiltonian indicates two terms: one for absorption and one for emission, questioning the sequence of these processes.
  • Another participant states that the conventional understanding is that a photon is absorbed before another photon is emitted, but cautions that models may not accurately reflect physical processes.
  • A different participant inquires whether excited electrons can emit radiation after the incident radiation, or if the process strictly follows absorption first, then emission.
  • One participant affirms that incoming radiation can indeed stimulate already excited electrons to decay, referencing the concept of "stimulated emission."

Areas of Agreement / Disagreement

Participants express differing views on the sequence of absorption and emission processes, with no consensus reached on whether emission occurs directly from incident radiation or only after absorption.

Contextual Notes

The discussion highlights uncertainties regarding the physical processes involved and the dependence on specific models, without resolving the complexities of the mechanisms at play.

hokhani
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When an electromagnetic wave is impinged on a semiconductor and we solve the perturbed Hamiltonian by taking into account the vector potential in the momentum term, two terms would add to the unperturbed Hamiltonian which one of them deals with absorption while the other with emission. I like to know whether the emission is made by the incident radiation itself, or first the radiation is absorbed then the excited electron would come back and radiate?
 
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The usual picture is that a photon gets absorbed and then another photon is radiated.

Careful though, a model need not follow the physical process.
If you have not measured it, then there may be a range of things that could have happened.
 
Simon Bridge said:
The usual picture is that a photon gets absorbed and then another photon is radiated.
If we have some electrons at higher levels before impinging, would they come down to the lower levels by emission after impinging? (Suppose that we have only two possible ways, absorption and emission by electrons)? Or first the photon is absorbed by an electron and then emission is only made by the excited electron when is coming back to lower levels?
 
Sure - if you have already excited electrons, the incoming radiation can prompt them to decay.
The process is called "stimulated emmission" ... you can look it up ;)
 
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