Electrons Absorbing Photons - Extra Energy

Click For Summary

Discussion Overview

The discussion revolves around the absorption of photons by electrons in atoms, particularly focusing on what happens when a photon has excess energy beyond what is required to excite an electron to a higher energy level. Participants explore concepts related to energy conservation, photon absorption, and the implications for the color of objects.

Discussion Character

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

Main Points Raised

  • One participant questions the fate of excess energy when a photon with more energy than needed for an electron transition is absorbed, suggesting it might be released as another photon.
  • Another participant asserts that photons are only absorbed if they have the exact energy required for an electron transition, indicating that excess energy would not result in absorption.
  • A participant challenges the idea that a photon with slightly more energy than required would not be absorbed, seeking clarification on the absorption process.
  • Discussion includes the concept of electronic transitions in monatomic gases, noting that transitions typically require photon energy to match energy state gaps, but can occur under certain conditions due to the uncertainty principle.
  • One participant introduces the idea of electronic Raman scattering, where excess energy can be carried away by a red-shifted photon, although this process is described as weak and not easily observed.
  • Another participant mentions that monoatomic gases can absorb photons with energies slightly different from the exact excitation energy due to factors like lifetime and Doppler broadening.

Areas of Agreement / Disagreement

Participants express differing views on whether photons with excess energy can be absorbed and what happens to that energy. Some agree that excess energy can lead to the emission of another photon, while others maintain that only photons with exact energy levels are absorbed. The discussion remains unresolved regarding the specifics of energy absorption and release.

Contextual Notes

There are limitations regarding the assumptions made about energy absorption, the definitions of energy states, and the conditions under which transitions occur. The discussion highlights the complexity of photon interactions with electrons and the role of various physical principles.

Who May Find This Useful

This discussion may be of interest to those studying atomic physics, quantum mechanics, or anyone curious about the interactions between light and matter, particularly in the context of color perception and energy transitions.

Legaldose
Messages
73
Reaction score
6
Okay, so when a photon travels near an electron orbiting some atom, the electron then absorbs the photon (given that it has enough energy) and causes the electron to jump up an energy level. My question is what happens when a photon has a little more than enough energy to bump up the electron, where does the remaining energy go? Is it correct to say that another photon gets released that carries the remaining energy? And if so, then is that partly why objects are certain colors? If I have this totally wrong please feel free to correct me. Thanks.
 
Physics news on Phys.org
objects are certain colours due to the fact that they REFLECT that colour of light. such that there phonons are opaque to that frequency.
a photon is absorbed by an atom causing it to be excited and an electron moves to a higher energy state. photons will only be absorbed by atoms if they have the exact energy required to go from one energy state to another. if not they simply won't be absorbed. and you are correct the energy is released in the form of another photon of the EXACT same energy as the original due to conservation of energy.
 
So you are saying that if it takes 1J to move an electron up an energy level, and a photon comes along that has 1.1J of energy, then the photon will not be absorbed?
 
For monatomic gases, it is fair to say that for practical purposes electronic transitions do not occur with appreciable intensity unless the photon frequency matches the gap between energy states - although this does not have to be "exact", due to the uncertainty principle.

Photons can,however, undergo electronic Raman scattering even in this situation (in other words, the transition takes place, and a red-shifted photon carries away the excess energy). Such transitions are rather weak, and not easily observed (laser or synchrotron sources are needed).

In molecules and condensed phases a variety of mechanisms exists to take up any excess photon energy with appreciable probability, leading to broad absorption lines (as seen in the UV-visible spectra taken in the chemistry lab).
 
Thanks gadong, this clears things up quite a bit for me. And even better, it makes good sense as well.
 
A sample of monoatomic gas can absorb photons with energies slightly different from the exact excitation energy, because of lifetime and Doppler broadening.
 

Similar threads

  • · Replies 18 ·
Replies
18
Views
2K
  • · Replies 11 ·
Replies
11
Views
3K
Replies
37
Views
6K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 14 ·
Replies
14
Views
2K
  • · Replies 23 ·
Replies
23
Views
5K
  • · Replies 20 ·
Replies
20
Views
10K
  • · Replies 1 ·
Replies
1
Views
2K