What is the Thomson cross section?
The Thomson cross section is σ_T = 6.6524587321e-29 m^2 (uncertainty ±6.0e-38). It is the classical scattering cross section of a free electron.
Open the interactive PhysRef tool →Key facts
| Value | 6.6524587321e-29 m^2 |
|---|---|
| Symbol | σ_T |
| Uncertainty | ±6.0e-38 m^2 |
| Relation | σ_T = (8π/3)·r_e^2 |
| Source | CODATA 2018 |
Frequently asked questions
What is the value of the Thomson cross section?
σ_T = 6.6524587321e-29 m^2, the cross section for low-energy photon scattering off a free electron.
How is the Thomson cross section defined?
σ_T = (8π/3)·r_e^2, using the classical electron radius r_e.
Where is it used?
In astrophysics and plasma physics, e.g. for radiation pressure and electron scattering opacity.
Related pages
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