Thomson cross section
E160626
The Thomson cross section is a fundamental physical constant that quantifies the effective area for low-energy (classical) scattering of electromagnetic radiation by a free charged particle, typically an electron.
All labels observed (2)
| Label | Occurrences |
|---|---|
| Thomson cross section canonical | 1 |
| Thomson scattering formula | 1 |
How this entity was disambiguated
This entity first appeared as the object of triple T1403725 — resolving that mention is where its identity was fixed. The disambiguator weighed these candidate entities and picked the highlighted one (or “None”, minting a new entity). This is how homonymy is resolved: the same surface form can point to different entities.
NED1
Entity disambiguation (via context triple)
gpt-5-mini-2025-08-07
Target entity: Thomson cross section Context triple: [CODATA recommended values of the fundamental physical constants, includesConstant, Thomson cross section]
-
A.
Klein–Nishina formula
The Klein–Nishina formula is a fundamental result in quantum electrodynamics that gives the differential cross section for Compton scattering of photons by free electrons, incorporating relativistic and quantum effects.
-
B.
Compton effect
The Compton effect is the increase in wavelength (and corresponding decrease in energy) of X-rays or gamma rays when they scatter off electrons, providing key evidence for the particle nature of light.
-
C.
Bethe formula for stopping power
The Bethe formula for stopping power is a fundamental equation in particle physics that quantifies the energy loss of fast charged particles as they pass through matter.
-
D.
Schwinger effect
The Schwinger effect is a quantum field theory phenomenon in which extremely strong electric fields can spontaneously create particle–antiparticle pairs from the vacuum.
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E.
TOTal Elastic and diffractive cross section Measurement
TOTal Elastic and diffractive cross section Measurement (TOTEM) is a CERN experiment at the Large Hadron Collider dedicated to precisely measuring proton–proton total, elastic, and diffractive cross sections at high energies.
- F. None of above. chosen
- G. Unsure - the case is ambiguous/there is not enough information to decide.
NED2
Entity disambiguation (via description)
gpt-5-mini-2025-08-07
Target entity: Thomson cross section Target entity description: The Thomson cross section is a fundamental physical constant that quantifies the effective area for low-energy (classical) scattering of electromagnetic radiation by a free charged particle, typically an electron.
-
A.
Klein–Nishina formula
The Klein–Nishina formula is a fundamental result in quantum electrodynamics that gives the differential cross section for Compton scattering of photons by free electrons, incorporating relativistic and quantum effects.
-
B.
Compton effect
The Compton effect is the increase in wavelength (and corresponding decrease in energy) of X-rays or gamma rays when they scatter off electrons, providing key evidence for the particle nature of light.
-
C.
Bethe formula for stopping power
The Bethe formula for stopping power is a fundamental equation in particle physics that quantifies the energy loss of fast charged particles as they pass through matter.
-
D.
Schwinger effect
The Schwinger effect is a quantum field theory phenomenon in which extremely strong electric fields can spontaneously create particle–antiparticle pairs from the vacuum.
-
E.
TOTal Elastic and diffractive cross section Measurement
TOTal Elastic and diffractive cross section Measurement (TOTEM) is a CERN experiment at the Large Hadron Collider dedicated to precisely measuring proton–proton total, elastic, and diffractive cross sections at high energies.
- F. None of above. chosen
Statements (43)
| Predicate | Object |
|---|---|
| instanceOf |
physical constant
ⓘ
scattering cross section ⓘ |
| appliesTo |
free charged particle
ⓘ
low-energy electromagnetic radiation ⓘ |
| CODATARecommended | true ⓘ |
| constantIn | SI units ⓘ |
| dependsOn | classical electron radius ⓘ |
| describes | scattering of electromagnetic waves by free electrons ⓘ |
| dimension | L^2 ⓘ |
| energyRegime | classical limit ⓘ |
| expression |
σ_T = (8π/3) (e^2 / (4π ε_0 m_e c^2))^2
ⓘ
σ_T = (8π/3) r_e^2 ⓘ |
| field |
classical electrodynamics
ⓘ
quantum electrodynamics ⓘ |
| frameOfReference | electron rest frame ⓘ |
| governs | classical radiation pressure on free electrons ⓘ |
| independentOf | photon frequency in classical limit ⓘ |
| interactionType | elastic scattering ⓘ |
| isLowEnergyLimitOf | Klein–Nishina formula ⓘ |
| isotropic | true ⓘ |
| namedAfter | J. J. Thomson ⓘ |
| occursIn | non-relativistic regime ⓘ |
| proportionalTo | square of classical electron radius ⓘ |
| relatedQuantity | differential scattering cross section ⓘ |
| relatedTo |
Compton effect
ⓘ
surface form:
Compton scattering
|
| relevantFor |
hot plasmas
ⓘ
ionized intergalactic medium ⓘ stellar interiors ⓘ |
| symbol | σ_T ⓘ |
| typicallyConsideredFor | electron ⓘ |
| unit | square metre ⓘ |
| usedIn |
Sunyaev–Zel’dovich effect calculations
ⓘ
X-ray astronomy ⓘ astrophysics ⓘ cosmic microwave background analysis ⓘ cosmology ⓘ plasma physics ⓘ radiative transfer ⓘ |
| usedToCompute |
mean free path for photon–electron scattering
ⓘ
optical depth to electron scattering ⓘ |
| validWhen | photon energy ≪ electron rest mass energy ⓘ |
| value | 6.6524587321×10^-29 m^2 ⓘ |
| valueUncertainty | 0.0000000060×10^-29 m^2 ⓘ |
How these facts were elicited
The pipeline generated the facts above by prompting gpt-5.1 with this entity's name + description and the instruction below.
Instruction
You are a knowledge base construction expert. Given a subject entity and a description of it, return factual statements that you know for the subject as a JSON list of dictionaries(triples), where keys must be "subject", "predicate" and "object". The number of facts may be very high, between 25 to 50 or more, for very popular subjects. For less popular subjects, the number of facts can be very low, like 5 or 10. # Requirements - If you don't know the subject at all, return an empty list. - If the subject is not a named entity, return an empty list. - Include at least one triple where predicate is "instanceOf". - Do not get too wordy. - Separate several objects into multiple triples with one object.
Input
Subject: Thomson cross section Description of subject: The Thomson cross section is a fundamental physical constant that quantifies the effective area for low-energy (classical) scattering of electromagnetic radiation by a free charged particle, typically an electron.
Referenced by (2)
Full triples — surface form annotated when it differs from this entity's canonical label.
CODATA recommended values of the fundamental physical constants
→
includesConstant
→
Thomson cross section
ⓘ
this entity surface form:
Thomson scattering formula