Radiative Transfer Trivial Mechanism

This can be an important process if the acceptor A absorbs in the wavelength region in which the donor D emits. The efiSciency of the process is determined by the quantum yield of D emission and by the optical density of A at the donor emission wavelength. The probability that an acceptor molecule wiH reabsorb the light varies as where R is the donor-acceptor separation. 

When D and A are similar molecules emission-reabsorption cannot be very important due to the usually small overlap of the emission and absorption spectra. Also, this mechanism should not be important for triplet-triplet energy transfer because of (a) low phosphorescence quantum yields in fluid solutions and (b) the low oscillator strengths for singlet-triplet absorption. 

Energy transfer by the trivial mechanism is characterized by (a) change in the donor emission spectrum (inner filter effect), (b) invariance of the donor emission lifetime, and (c) lack of dependence upon viscosity of the medium. 

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The radiative or trivial mechanism of inter-molecular energy transfer can be expressed as a sequence of two independent steps... 

The intermolecular transfer of electronic excitation energy is a common phenomenon in photochemistry. It is called photosensitization and may occur by a number of mechanisms, both radiative and nonradiative. In the radiative process, also called the trivial mechanism, the acceptor, A, absorbs a quantum emitted by a donor, D (Equations 13.11 and 13.12). 

Several different mechanisms of electronic energy transfer are believed to operate under different circumstances. The first of these is the so-called trivial mechanism of radiative transfer, which can be represented by the processes... 

There is also a radiative energy transfer mechanism termed the trivial mechanism of energy transfer. It is accomplished through radiative deactivation of a luminophore donor and reabsorption of the emitted photon by a chromophoric acceptor. There is no direct interaction between the excited donor and the ground... 

Energy transfer may occur via radiative or nonradiative mechanisms. Radiative energy transfer is often described as the "trivial" mechanism... 

Clearly, such an energy transfer can occur over any donor-acceptor distance. Photochemical processes induced on the Earth by sunlight are extreme examples of long-range radiative energy transfer. In this "trivial" mechanism, the acceptor molecule has no way to influence the emission ability of the donor, but merely intercepts the emitted photon before the latter can be observed. The "trivial" energy transfer mechanism can be readily explained in terms of the laws of optics and of light absorption and emission. 

There is a third mechanism of energy transfer known as the trivial or radiative energy-transfer mechanism. Here, energy is transferred by radiative deactivation of a donor and reabsorption of this emitted light by an acceptor molecular entity. This mechanism is less important in supramolecular chemistry and is not dealt with in further detail here. 

The first polymer acts as donor and the second polymer acts as acceptor. The two polymers show a strong overlap between the donor emission spectrum and the acceptor absorption spectrum, both in solution and films. The emission decay of neat PVK is much slower than that of the acceptor, which indicates a non-radiative energy transfer process. The steady-state photoluminescence spectra of PVK exhibit an intensity decrease in the presence of the donor, however, the decrease in the PVK lifetime does not follow the same trend upon increasing the donor concentration. Therefore, it has been assumed that the intensity decrease is more strongly correlated with the trivial energy transfer than with a Forster energy transfer mechanism [92]. 

Excited energy transfer among chromophores is one of the most ftmdamental photophysical processes. According to the mechanism the excited energy transfer is classified into 1.) radiative trivial type, 2.) nonradiative Forster type [286], and 3.) nonradiative Dexter type [285]. 

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