rotational diffusion coefficient

Defined by the equation:

$D θ = t θ ∂ ( f θ Φ ) ∂ θ sin ⁡ θ$

where $f θ Φ sin ⁡ θ d θ d Φ$ is the fraction of particles whose axes make an angle between $θ$ and $θ + d θ$ with the direction $θ = 0$ , and have an azimuth between $Φ$ and $Φ + d Φ$ ; $t θ d Φ$ is the fraction of particles having an azimuth between $Φ$ and $Φ + d Φ$ whose axis passes from values $< θ$ to values $> θ$ in unit time. The axis whose rotational diffusion is considered has to be clearly indicated.

Source:

PAC, 1972, 31, 577 (Manual of Symbols and Terminology for Physicochemical Quantities and Units, Appendix II: Definitions, Terminology and Symbols in Colloid and Surface Chemistry) on page 617

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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. https://doi.org/10.1351/goldbook.

Last update: 2014-02-24; version: 2.3.3.

DOI of this term: https://doi.org/10.1351/goldbook.R05411.

Original PDF version: http://www.iupac.org/goldbook/R05411.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 The PDF version is out of date and is provided for reference purposes only.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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rotational diffusion		rotational frequency, $f rot$ in centrifugation