radiative energy transfer

Transfer of excitation energy by radiative deactivation of a donor molecular entity and reabsorption of the emitted radiation by an acceptor molecular entity.

Notes:

Radiative transfer results in a decrease of the donor fluorescence intensity in the region of spectral overlap. Such a distortion of the fluorescence spectrum is called inner-filter effect.
Radiative energy transfer depends on the shape and size of the vessel utilized and on the configuration of the latter with respect to excitation and observation.
The fraction $a$ of photons emitted by D and absorbed by A is given by
$a = 1 Φ D 0 ∫ λ I λ D λ 1 − 10 − ɛ A λ c A l ⁢ d λ$
where $c A$ is the molar concentration of acceptor, $Φ D 0$ is the fluorescence quantum yield in the absence of acceptor, $l$ is the thickness of the sample, $I λ D λ$ and $ɛ A λ$ are the spectral distribution of the spectral radiant intensity of the donor fluorescence and the molar decadic absorption coefficient of the acceptor, respectively, with the normalization condition $Φ D 0 = ∫ λ I λ D λ ⁢ d λ$ .

For relatively low absorbance, $a$ can be approximated by
$a = 2.3 Φ D 0 c A l ∫ λ I λ D λ ɛ A λ ⁢ d λ$
where the integral represents the overlap between the donor fluorescence spectrum and the acceptor absorption spectrum.

Source:

PAC, 2007, 79, 293 (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 411