Cross section of ion excitation in ion-ion collision

The “effective Feynman diagram” technique introduced in a previous paper is used to express the cross section of ion excitation in ion-ion collisions $\text{(A + B → A}{}^1\text{+ B)}$ in terms of the corresponding photon resonance absorption $\text{(hv + A → A}{}^1\text{)}$ and Thomson-scattering (hv + B → hv + B) cross sections. The result is checked for the process He⁺ + H(1s) → He⁺ + H(2p) with experiment and very good agreement is obtained.