After Diffusion
Once diffusion has taken place, the particles keep moving because they still have kinetic energy. In fact, particles never stop moving and retain their kinetic energy unless they are exposed to absolute zero (-459º Fahrenheit, -273º Celsius, or 0 Kelvin) where there is no kinetic energy at all.
However, after diffusion the particles are evenly scattered and there is no longer an area of high or low particle concentration.
The diagram would now look like this:
