Rayleigh Scattering – Thomson Scattering
Rayleigh scattering, also known as Thomson scattering is the low-energy limit of Compton scattering. The particle kinetic energy and photon frequency do not change as a result of the scattering. Rayleigh scattering occurs as a result of an interaction between an incoming photon and an electron, the binding energy of which is significantly greater than that of the incoming photon. The incident radiation is assumed to set the electron into forced resonant oscillation such that the electron re-emits radiation of the same frequency but in all directions. In this case, the electric field of the incident wave (photon) accelerates the charged particle, causing it, in turn, to emit radiation at the same frequency as the incident wave, and thus the wave is scattered. Rayleigh scattering is significant up to ≈ 20keV and like Thomson scattering, is elastic. The total scattering cross section becomes a combination of the Rayleigh and Compton bound scattering cross sections. Thomson scattering is an important phenomenon in plasma physics and was first explained by the physicist J. J. Thomson. This interaction has great significance in the area of X-ray crystallography.
Interaction of X-rays with Matter
Although a large number of possible interactions are known, there are three key interaction mechanisms with matter. The strength of these interactions depends on the energy of the X-rays and the elemental composition of the material, but not much on chemical properties, since the X-ray photon energy is much higher than chemical binding energies. The photoelectric absorbtion dominates at low-energies of X-rays, while Compton scattering dominates at higher energies.
- Photoelectric absorption
- Compton scattering
- Rayleigh scattering