Term: Förster excitation transfer (dipole–dipole excitation transfer)
https://doi.org/10.1351/goldbook.F02488

Definition:
A mechanism of excitation transfer which can occur between molecular entities separated by distances considerably exceeding the sum of their van der Waals radii. It is described in terms of an interaction between the transition dipole moments (a dipolar mechanism). The transfer rate constant kD → A is given by: \[k_{\ce{D -> A}} = \frac{K^{2}J \pu{8.8E-28 mol}}{n^{4} \tau_{0} r^{6}}\] where K is an orientation factor, n the refractive index of the medium, τ 0 the radiative lifetime of the donor, r the distance (cm) between donor (D) and acceptor (A), and J the spectral overlap (in coherent units cm^6 mol^-1) between the absorption spectrum of the acceptor and the fluorescence spectrum of the donor. The critical quenching radius, r 0, is that distance at which kD → A is equal to the inverse of the radiative lifetime.

Related Terms:
1) dexter excitation transfer (http://doi.org/10.1351/goldbook.D01654).
2) energy transfer (<em>in photochemistry</em>) (http://doi.org/10.1351/goldbook.E02116).
3) radiative energy transfer (<em>in photochemistry</em>) (http://doi.org/10.1351/goldbook.R05063).
4) excitation transfer (<em>in photochemistry</em>) (http://doi.org/10.1351/goldbook.E02256).
5) rate constant (<em>in photochemistry</em>) (http://doi.org/10.1351/goldbook.O04322).
6) refractive index (<em>in photochemistry</em>) (http://doi.org/10.1351/goldbook.R05240).
7) radiative lifetime (<em>in photochemistry</em>) (http://doi.org/10.1351/goldbook.R05064).
8) spectral overlap (<em>in photochemistry</em>) (http://doi.org/10.1351/goldbook.S05818).
9) absorption spectrum (<em>in photochemistry</em>) (http://doi.org/10.1351/goldbook.A00043).
10) fluorescence (<em>in photochemistry</em>) (http://doi.org/10.1351/goldbook.F02453).

Source: PAC, 1996, 68, 2223. 'Glossary of terms used in photochemistry (IUPAC Recommendations 1996)' on page 2243 (https://doi.org/10.1351/pac199668122223)

Citation: 'Förster excitation transfer (dipole–dipole excitation transfer)' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.F02488

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