Thomson cross section for low-energy scattering

thomsonCrossSection is the classical cross section for scattering electromagnetic radiation by a free electron at low photon energy.

Use

It provides a reference area in plasma and astrophysical scattering estimates. It depends on the electronMass, elementaryCharge, and electromagnetic constants.

Caveats

It applies in the classical, low-energy limit. At high photon energies, quantum Compton scattering is required. Treat a cross section as area, not a geometric particle size; use multiply with number density and path length only in the appropriate model.