Excitation of electrons by electromagnetic source

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Discussion Overview

The discussion revolves around the excitation of electrons by electromagnetic sources, specifically focusing on the energy requirements for ionization and excitation of electrons in atoms. Participants explore the conditions under which photons can interact with bound electrons, including the implications of using photons with energies lower than the ionization threshold.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether a photon with less energy than the ionization energy can still add energy to an electron and whether the electron would re-emit the photon with less energy.
  • Another participant asserts that to excite an electron to a higher orbital, the photon must have the exact energy corresponding to that orbital, although they note that "exact" is a relative term in practice.
  • There is a claim that if a photon has energy close to an energy gap, it may be absorbed, promoting an electron to a higher energy state, while a photon with insufficient energy would simply scatter.
  • One participant argues against the possibility of using two photons of lower energy to achieve the same excitation as a single photon with the exact energy, suggesting that this would affect the absorption spectra.
  • Another participant provides links to external sources for further reading on multi-photon absorption, indicating a search for more reliable information.

Areas of Agreement / Disagreement

Participants express differing views on the energy requirements for electron excitation and the feasibility of multi-photon absorption, indicating that the discussion remains unresolved with multiple competing perspectives.

Contextual Notes

There are limitations regarding the assumptions made about photon energy and electron excitation, as well as the definitions of terms like "exact" in the context of energy levels. The discussion also touches on the precision of absorption spectra and the implications of using different energy sources.

Northprairieman
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If you hit a bound electron with a photon corresponding to that electron's ionization energy, you ionize the electron. What if you hit the electron with a photon with less energy? Will the photon still add its energy to the electron? Will the electron re-emit the photon with less energy?

Do you always need the exact amount of energy in a photon to excite an electron to a higher orbital? Can you say hit an electron with 2 photons of less energy to raise it to the same orbital as would be done by a photon with the exact energy of the next orbital?
 
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If you hit a bound electron with a photon corresponding to that electron's ionization energy, you ionize the electron.
Atoms may be ionized, not fundamental charges. A photon carrying the appropriate energy or higher may ionize an atom by ejecting an electron.

What if you hit the [atom] with a photon with less energy?
If the photon energy is close to an energy gap, then the photon may be absorbed, an electron is promoted to a higher energy state and we say that the atom is "excited" - otherwise the photon just scatters.

Do you always need the exact amount of energy in a photon to excite an electron to a higher orbital?
Yes - though IRL there is no such thing as "exact".
This is why the absorption spectra lines are so precise. The width of the lines is usually more to do with the spectrograph than the atoms.

Can you say hit an electron with 2 photons of less energy to raise it to the same orbital as would be done by a photon with the exact energy of the next orbital?
No. Not commonly. If they did, think what the effect on the absorption spectra would be.

[edit] well done
Notice that the article talks about molecular excitation not atomic excitation - which is what you asked about. In general, wikipedia is a poor place to learn science.
 
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