What Are the Rules for Electron Absorption and Emission in Atoms?

Click For Summary

Discussion Overview

The discussion revolves around the rules governing electron absorption and emission in atoms, particularly focusing on the threshold frequency for electron ejection, the nature of absorption and emission frequencies, and the behavior of electrons when interacting with photons. The scope includes theoretical concepts related to atomic physics and quantum mechanics.

Discussion Character

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

Main Points Raised

  • One participant suggests that electrons are only ejected from atoms when bombarded with electromagnetic waves above a certain threshold frequency, with the intensity of light affecting the number of electrons ejected.
  • Another participant asserts that electrons can absorb any frequency above the threshold, but questions remain about the specifics of this absorption.
  • There is a claim that emission and absorption frequencies are not limited to discrete values due to the uncertainty principle, which allows for a range of energies rather than exact values.
  • One participant challenges the idea that electrons can absorb higher energy photons and then re-emit lower energy photons, stating that the energy of emitted or absorbed photons must equal the difference between two energy levels in the atom.
  • A later reply introduces the idea that while electrons cannot absorb fractional energy, the atom as a whole can, since it is not bound in the same way as the electrons.

Areas of Agreement / Disagreement

Participants express differing views on the nature of absorption and emission frequencies, particularly regarding the discreteness of these values and the behavior of electrons in relation to photon energy. There is no consensus on some of the fundamental aspects discussed.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about the nature of bound and unbound particles, as well as the implications of the uncertainty principle on spectral lines and energy absorption.

DeG
Messages
23
Reaction score
0
This is my understanding; please, correct me if I'm wrong.
If you bombard an atom with em-waves they will never break loose electrons until a certain threshold frequency. At this point the intensity of the light (or the amount of photons) striking the atom is proportional to the number of electrons ejected. The additional energy in the photon, beyond the energy required to break the bond, goes into kinetic energy of the electron. Electrons also absorb and emit specific frequencies of light when jumping between specific orbitals.
Does the threshold frequency only apply to breaking an electron loose, i.e. out of the atoms orbitals, and does this mean they can absorb any frequency above the threshold? Do the emission/ absorption frequencies only happen at discrete, exact values (versus a distribution of values)? Can they absorb higher energy photons, jump orbitals, then take the remaining energy as kinetic or even re-emit it as a lower frequency photon?
Thanks
 
Physics news on Phys.org
I am not an expert, but I will take a shot at answering your questions.

does this mean they can absorb any frequency above the threshold?

Yes. Only bound particles are restricted to carrying specific amounts of energy.

Do the emission/ absorption frequencies only happen at discrete, exact values?

No. The uncertainty principle dictates that a process with a known amount of time has an uncertain amount of energy. Spectral lines are not infinitely thin. Instead, there is a very small range in which the energy can be absorbed/emitted.

Can they absorb higher energy photons, jump orbitals, then take the remaining energy as kinetic or even re-emit it as a lower frequency photon?

If the electron is still bound, no. The energy of a photon emitted or absorbed can only be equal to the difference between two energy levels in the atom.

It actually took me some research to find these answers, so I hope you like them.
 
Nice, thank you very much. That all makes a lot of sense.
 
DeG said:
Nice, thank you very much. That all makes a lot of sense.

You're welcome. I guess I should also add that, while the electron can't absorb a fractional amount of energy from a photon, the atom as a whole can, since the atom itself is not bound.

https://www.physicsforums.com/showthread.php?t=515982
 

Similar threads

Undergrad Why don't absorption and emission spectra "cancel out"?
  • · Replies 8 ·
Replies
8
Views
4K
High School Why are absorption spectra continuous?
  • · Replies 9 ·
Replies
9
Views
8K
Graduate Trying to understand emission and absorption
  • · Replies 1 ·
Replies
1
Views
3K
Undergrad Only certain emission lines show up in absorption spectrum
  • · Replies 4 ·
Replies
4
Views
3K
Undergrad Radiative and Nonradiative Transitions
  • · Replies 3 ·
Replies
3
Views
4K
Undergrad A photon absorption/emission by an atom
  • · Replies 4 ·
Replies
4
Views
4K
Undergrad How does detuned laser frequency affect atomic dipole forces?
  • · Replies 10 ·
Replies
10
Views
3K
Graduate Blackbody emission and absorption
  • · Replies 2 ·
Replies
2
Views
3K
High School Why is an electric arc needed for spectroscopy of clear gases?
  • · Replies 4 ·
Replies
4
Views
3K
Undergrad Absorption line spectra and emission line spectra
  • · Replies 5 ·
Replies
5
Views
7K