Title: out-scattering
Long Title: IUPAC Gold Book - out-scattering
DOI: 10.1351/goldbook.14030
Status: current

Definition
Physical process by which the incoming electromagnetic radiation is forced to deviate from a straight trajectory by non-uniformities in the medium.

Notes
1) Physical phenomenon taking into account scattered radiative energy from the rays in the direction \(\mathit{\Omega}\) considered in the radiative transfer equation (RTE) into any direction \(\mathit{\Omega}'\).
2) Mathematical definition: \({\rm{Sc}}_{\rm{out}} = \sigma_{\lambda} (\boldsymbol{x},t) L_{\mathit{\Omega},\lambda} (\boldsymbol{x},t)\) where \(\boldsymbol{x}\) is the coordinate in a three-dimensional space in the path of the beam, \(t\) is the time coordinate, \(\sigma_{\lambda} (\boldsymbol{x},t)\) is the space- and time-dependent linear napierian scattering coefficient, \(L_{\mathit{\Omega},\lambda} (\boldsymbol{x},t)\) is the incident space- and time-dependent radiance in the direction \(\mathit{\Omega}\). SI unit is \(\pu{W sr-1 m-4}\). Common unit is \(\pu{W sr-1 cm-3 nm-1}\).
3) The mathematical definition in photon terms is: \({\rm{Sc}}_{\rm{out}} = \sigma_{\lambda} (\boldsymbol{x},t) L_{\rm{p},\mathit{\Omega},\lambda} (\boldsymbol{x},t)\) with \(L_{\rm{p},\mathit{\Omega},\lambda} (\boldsymbol{x},t)\) the incident space- and time-dependent photon radiance. SI unit is \(\pu{s-1 sr-1 m-4}\) in photon number basis and \(\pu{mol s-1 sr-1 m-4}\) in chemical amount basis. Common unit in photon number basis is \(\pu{s-1 sr-1 cm-3 nm-1}\) and \(\pu{einstein s-1 sr-1 cm-3 nm-1}\) in chemical amount basis.

Related Terms
- in-scattering: https://goldbook.iupac.org//terms/view/14023
- radiative transfer equation: https://goldbook.iupac.org//terms/view/14077

Source
- PAC, 2011, 83, 931. 'Glossary of terms used in photocatalysis and radiation catalysis (IUPAC Recommendations 2011)' on page 962 (https://doi.org/10.1351/PAC-REC-09-09-36)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/14030/html
- json: https://goldbook.iupac.org/terms/view/14030/json
- xml: https://goldbook.iupac.org/terms/view/14030/xml

Citation: Citation: 'out-scattering' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.14030
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Accessed: 2026-06-28T20:56:50+00:00