Photon excitation to full orbitals

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Discussion Overview

The discussion revolves around the concept of photon excitation in relation to electron orbitals, particularly focusing on what occurs when an electron is excited to an already filled orbital. The scope includes theoretical implications, principles from quantum mechanics, and references to specific phenomena like spectral hole burning.

Discussion Character

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

Main Points Raised

  • One participant questions the implications of exciting an electron to a filled orbital, suggesting that it may lead to orbital splitting or hybridization to comply with the Pauli exclusion principle.
  • Another participant asserts that it is not possible to excite an electron to a filled orbital.
  • A follow-up query raises whether a photon with energy corresponding to a specific transition would be absorbed if a higher energy level is filled.
  • A participant provides an example involving fluorine, noting that absorption occurs differently in its ionized versus neutral states, indicating that filled orbitals prevent absorption of certain photon energies.
  • One participant introduces the concept of spectral hole burning, explaining that if the upper absorption level is not full, the material can still absorb light, but selectively filling upper levels can make it transparent to specific frequencies.
  • Another participant clarifies that spectral hole burning applies only in contexts where there is initial absorption, emphasizing the filled nature of orbitals in their example.
  • A participant highlights the relevance of Pauli's exclusion principle, stating that no two electrons can occupy the same quantum state, reinforcing the impossibility of exciting an electron to a filled orbital.
  • One participant notes that the discussion may be more aligned with general chemistry topics, reflecting on their educational background.

Areas of Agreement / Disagreement

Participants express disagreement regarding the possibility of exciting electrons to filled orbitals, with some asserting it is impossible while others explore the implications of such scenarios. The discussion remains unresolved with multiple competing views on the topic.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about electron configurations, the definitions of filled orbitals, and the specific conditions under which photon absorption occurs. These factors remain unresolved.

ngc2024
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In introductory physics and chemistry, photon excitation is usually illstrated with a simple hydrogen molecule. I am wondering what happens if an electron is excited to an orbital that is already full. Would the orbital split up into different energy levels as hybridisation, so as not to violate the pauli exlusion principle?
 
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You can't excite an electron to a filled orbital.
 
So that means that a photon with energy corresponding to the energy difference between, say n=1 and n=2, would not be absorbed if n=3 is filled?
 
ngc2024 said:
So that means that a photon with energy corresponding to the energy difference between, say n=1 and n=2, would not be absorbed if n=3 is filled?
These numbers are not quite correct. But say that you have F- in the electronic configuration 1s22s22p6: even if you have photons of energy E2p-E1s, there will be no absorption, while you would have absorption for neutral fluorine.
 
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The phenomenon is called Spectral Hole Burning. If the upper absorption level is not full, the material will absorb the light. But you can selectively fill upper levels and make the material transparent to that particular frequency. Here is a reference:
https://en.wikipedia.org/wiki/Spectral_hole_burning
 
Chandra Prayaga said:
The phenomenon is called Spectral Hole Burning.
Just to be clear: while spectral hole burning is a manifestation of what we are discussing, it applies only to cases where there is initially absorption. In the example I mentioned, the orbitals were already filled.
 
Thank you both - that is very interesting!
 
It has to do with Pauli's exclusion principle. No two electrons can occupy the same quantum state. So you cannot excite an electron to a filled orbital.
Note: Pauli's exclusion principle does not apply only to electrons but to an entire class of particles- fermions.
 
DrClaude said:
Just to be clear: while spectral hole burning is a manifestation of what we are discussing, it applies only to cases where there is initially absorption. In the example I mentioned, the orbitals were already filled.
Yes. All that has happened in your case is that you are half way through the process.
 
  • #10
Not to be offtopic, but isn't this more of a general chemistry related question? This is exactly what I learned in my chemistry class.
 

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