What is the collision probability for an energetic photon in free space?

[Ponderer]

Hi. Does anyone know the probability of an energetic photon interacting with ions in free space if we know the ion gas density and the photons wavelength? I'm trying to find out if the energetic photon is treated like a particle where its size is relative to it's wavelength. In other words, is it similar to the collision probability of a particle being shot inside a particle gas chamber? Thanks!

 

[Derek Potter]

It definitely cannot be treated as a classical collision. The full treatment would require stuff (QED/QFT) which is way beyond me. The size that you are after is the effective cross sectional area for the collision and typically peaks at certain energies where the available energy from the collision matches the energy required to excite the ion. It has nothing to do with the wavelength.

 

[mathman]

Photon interaction is very much dependent on the identity of the ions - spectral lines.

 

[Ponderer]

Yes that's what I thought, but was just wondering if it can be made to show results like a particle. If for example we use electrons for the ions, then I was wondering if the probability for interaction was relative to the gamma rays wavelength.

 

[mathman]

https://en.wikipedia.org/wiki/Klein–Nishina_formula

try the above.