Chapter 4

# Particle scattering

### Fondamental : Fick's law and equation of particle scattering

Fick's three-dimensional law : with the coefficient of scattering and the particle density.

This law shows that scattering can only take place in a medium where the particle density is not uniform.

Moreover, the gradient being oriented towards the increasing , the - symbol in Fick's law indicates that particles spontaneously scatter from the more concentrated places to the less concentrated ones.

Let's determine the one-dimensional equation of scattering without internal source of creation of particles.

A reasoning similar to the one of thermal transfers (we write the conservation of matter considering a cube, which has a volume ) : It results in the equation of conservation of matter : Using Fick's law, we obtain the one-dimensional equation of scattering : In three dimensions, we have (see the lesson about "Vector calculus") : And the equation of scattering (without source) : ### Attention : Fick's law and equation of particle scattering

Fick's law : Equation of scattering (without source) : Previous
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