Compton Scattering: What is the Difference from Electron-Photon Absorption?

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Discussion Overview

The discussion revolves around the differences between Compton scattering and photon absorption by electrons, exploring the mechanisms involved in each process and the conditions under which they occur. The scope includes theoretical aspects of photon interactions with free electrons and atoms.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant notes that Compton scattering involves a photon interacting with a free electron, which can change the electron's momentum regardless of the photon's energy being small.
  • Another participant clarifies that photon absorption is a quantum mechanical process that occurs in atoms, where the energy of the photon must match the energy difference between electron states in the atom for absorption to happen.
  • A further distinction is made that Compton scattering does not require the photon to meet a resonance condition, unlike photon absorption, which depends on specific energy levels.
  • One participant expresses a need for calculated scattering cross sections related to Compton scattering, indicating a desire for quantitative analysis before applying quantum field theory.

Areas of Agreement / Disagreement

Participants present differing views on the conditions and mechanisms of photon interactions, indicating that there is no consensus on the nuances between Compton scattering and photon absorption.

Contextual Notes

There are limitations in the discussion regarding the definitions of terms like "free electron" and "energy difference," as well as the specific conditions under which each process occurs, which remain unresolved.

Who May Find This Useful

This discussion may be useful for students and researchers interested in the interactions of photons with matter, particularly in the context of quantum mechanics and particle physics.

luxiaolei
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Hi all. Here is the question:

Compton scattering I understood is, any wavelength phton can kick an electron, hecnce change its momentum.

However, I also learned in the electron phton absorption process, if the photon's energy smaller than the energy difference between the two states of the electron, it will simply passing through electron.

What is the wrong here? Thanks a lot in advance.
 
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There are many different processes where photons interact with matter.
 
The first one is basically a process between photons and a free electron or a free nucleus.

The second one is a quantum mechanical process between photons and an atom. When you say the energy difference between states of electron, I think you mean energy difference between states of the ATOM. Of course, the electrons are situated at different states in an atom.
 
Compton scattering is scattering off of free electrons. This means the electron can absorb an arbitrarily small quantum of energy (and momentum), so it is quite different from the resonance condition about photon absorption that you stated.
 
I need to find a number of calculated scattering cross section of Compton scattering before using quantum field theory.
anyone can help me? My email address is: nghuuha210@gmail.com
 

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