A energy transfer

FIGURE 3.21 (a) Energy transfer mechanisms of phosphorescent dye as a sensitizer and (b) the EL external efficiency of the DCM2 doped devices. (From Baldo, M.A., Thompson, M.E., and Forrest, S.R., Nature, 403, 750, 2000. With permission.)... 

The nomenclature relating to electronic energy transfer is such that it is named according to the multiplicity of D and A as D —A energy transfer, common examples being ... 

Since the excited-state donor molecules are initially produced by photoexcitation and the energy is transferred to A, energy transfer is also referred to as the photosensitisation of A or the quenching of D. ... 

Fig. 18. Light-conversion photochemical molecular device, consisting of two components, a light collector (or antenna, lightabsorbing groups A) and a light emitter E, and performing a three-step process absorption (A), energy transfer (ET), and emission (E).

Lamola A. Energy transfer in solution theory and applications. Energy Trans. Organ. Chem. 1969 14 17-132. 

A very interesting series has been prepared and studied by Balzani, Belser, De Cola and co-workers [82], in which Ru(bpy)3 and Os(bpy)3 end groups are connected by three, five or seven phenylene units, the metal-metal distance ranging from 24 to 42 A. Energy transfer is deduced from the observed quenching of the Ru(II) phosphorescence, with a parallel sensitization of the Os(II) phosphorescence. Energy transfer rate constants vary from 6.7 x 10 s for n = 3 to 1.3 x 10 s for = 7 at 293 K in acetonitrile, and a decay rate of —0.32 A was established for the rate constants, corresponding to -0.16 A for the matrix elements. 

Andersson PO, Cogdell RJ and Gillbro T (1996) Femtosecond dynamics of carotenoid to bacteiiochlorophyU a energy transfer in the light harvesting antenna complexes from the purple bacterium Chromatium purpuratum. Chem Phys 210 195-217... 

III. DYNAMICS OF UNIMOLECULAR REACTIONS A. Energy Transfer During Unimolecular Reaction... 

A. Energy Transfer from Fuels through Oxidative Phosphorylation... 

Fi >. U. Eneigy transfer from a sensiiiser S to an activator A. Energy transfer is indicated by E.T. For further nouition, see Hg. 1.1... 

Energy transfer as described by Eq. (.5.1) is nonradiative energy transfer. The Occurrence of nonradiative energy transfer can be detected in several ways. If the excitation spectrum of the A emission is measured, the absorption bands of S will be found as well, since excitation of S yields emission from A via energy transfer. If S is excited selectively, the presence of A emission in the emission spectrum points to S A energy transfer. Finally, the decay time of the S emission should be shortened by the presence of nonradiative energy transfer, since the transfer process shortens the life time of the excited state S. ... 

Figure 1. Representation of the "antenna effect" for (a) energy transfer between chromophores dissolved in film and (b) sensitization of exciton state. The shaded circles represent the chromo-phore while the open circles are non-absorbing pendent groups (which potentially can be sensitized). R represents a "reaction center".

Energy transfer is typically measured by a decrease in the donor lifetime and, in the rapid diffusion limit, is a sensitive function of closest approach. Energy transfer based on a Forster dipole-dipole mechanism is proportional to a in three dimensions and a in two dimensions (e.g., on membranes), where a is the distance of closest approach. If the distance of closest approach is less than 10 or 11 A, energy transfer is dominated by a Dexter type exchange mechanism owing to overlapping wave functions between the donor and acceptor. The exact distance of closest approach then becomes difficult to measure. 

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