The multiphoton cross sections verse the number of exchanged photons (l) in the laser-assisted processes of electron scattering with impact energy of T i = 0.1 mc 2 = 0.0511 MeV . The scattering angels are θ = 1 ° for (a) Mott scattering, (b) electron–proton scattering, and (c) e– μ + scattering. The laser field is linearly polarized along the incident direction of the electron, the field intensity is ε 0 = 0.1 = 5.14 × 10 8 V · cm − 1 , and the photon energy ℏ ω = 1.17 eV .