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Rayleigh ratio

The quantity used to characterize the scattered intensity at the scattering angle θ, defined as R θ = i θ r 2 I f V, where I is the intensity of the incident radiation, i θ is the total intensity of scattered radiation observed at an angle θ and a distance r from the point of scattering and V is the scattering volume. The factor f takes account of polarization phenomena. It depends on the type of radiation employed.
  1. For light scattering, dependent on the polarization of the incident beam, f = 1 for vertically polarized light, f = cos 2 ⁡ θ for horizontally polarized light and f = 1 + cos 2 ⁡ θ 2 for unpolarized light.
  2. For small-angle neutron scattering, f = 1.
  3. For small-angle X-ray scattering, f ≈ 1, if θ < ca. 5 °.
Notes:
  1. The dimension of R θ is length −1.
  2. In small-angle neutron scattering the term cross-section is often used instead of R θ; the two quantities are identical.
  3. An alternative recommended symbol is R θ.
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Cite as:
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8. doi:10.1351/goldbook.
Last update: 2014-02-24; version: 2.3.3.
DOI of this term: doi:10.1351/goldbook.R05159.
Original PDF version: http://www.iupac.org/goldbook/R05159.pdf. The PDF version is out of date and is provided for reference purposes only. For some entries, the PDF version may be unavailable.
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