Figure 1.

This graphic shows the Compton scattering process for incoming linear polarized photons with respect to the scattering plane ϕ = ϕ′. The component perpendicular to the scattering plane does not undergo a change in the Compton process. The polarisation component in the scattering plane has to change since the direction of motion changes and the polarisation components have to be perpendicular to the direction of motion. In our particular reference frame by defining H to be the polarisation component in the scattering plane and V being the component perpendicular to the scattering plane, we find from formula (7) the following transition amplitudes H → H′:cos $\tilde{\mathrm{\Theta }}$, V → V′:−1, H → V′:0, V → H′:0.