Dipole resonance transfer

Expressing the transition moments in terms of measurable quantities allows the Forster transfer rate to be written in the form  

From the above equations, it can be seen that in dipole resonance transfer, the rate of transfer is dependent on the fluorescence intensity and on the fluorescence lifetime of the donor, as well as on the spectral overlap between the fluorescence of the donor and the absorbance of the acceptor. Two very important features of this transfer mechanism are the sixth-power dependence on the separation of the two molecules as well as the fact that it is possible to transmit energy by resonance transfer over distances of up to 50 A, a distance corresponding to several molecular diameters.  

The tendency for energy transfer between a pair of molecules in resists is characterized by a critical distance Rq at which the rate of energy transfer and the rate of spontaneous deactivation of the donor are equal. This leads to a con- 

The transfer rate for a given molecular separation / in a resist matrix can be written in the following form  

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Another estimate of transfer efficiency using spectral data may be obtained from Dexter s (4) formula for dipole-dipole resonance transfer,... 

DIPHTHERIA TOXIN DIPOLAR BOND DIPOLE-DIPOLE INTERACTION NONCOVALENT INTERACTLONS Dipole-dipole resonance energy transfer, FLUORESCENCE... 

The radial dependence of the fluorescence-quenching interaction between terbium, holmium, and neodymium in aqueous chloride solution was examined by Holloway and Kestigian (108a). From the concentration dependencies of the fluorescence lifetimes, they concluded that the probability for quenching interaction falls off as 1/r6, where r is the average spacing between the ions. If the mechanism of resonance transfer is assumed, the observed radial dependence implies a dipole-dipole interaction. 

Dimole absorption and emission, 247 Dioxetane formation, 253 Donor-acceptor energy levels, 201 property, energies of, 289 Dipole-dipole resonance energy transfer, 192, 193... 

Optical excitation transfer can occur between molecules as much as 10 nm apart when the dipole-dipole coupling between molecules (one excited "photon donor" chromophore, the other an unexcited "photon acceptor" chromophore) by a mechanism known as Forster79 resonance transfer or fluorescence resonance energy transfer (FRET) its characteristic dependence on the distance r between the two chromophores is r 6. 

Characteristic Lengths Associated with Dipole-Dipole Resonant S-P Excitation Transfer (pi = d2/flv)... 

Figure 5-11. Schematic representation of a group of pigments in a photosystem core that harvests a light quantum (hv) and passes the excitation to a special trap chlorophyll. Short straight lines indicate the inducible dipoles of chlorophyll molecules and the wavy lines indicate resonance transfer. In the reaction center an electron (e ) is transferred from the trap chi to some acceptor (A in the reduced form) and is then replaced by another electron coming from a suitable donor (D+ in the oxidized form).

In the first section of this article we describe resonant dipole-dipole energy transfer collisions between Rydberg atoms. As we shall see, very subtle features can be discerned in these collisions, and they are a good starting point for the development of an understanding of dipole-dipole interactions in a frozen Rydberg gas. 

By resonance transfer, we mean two radiators which are radiating at the same frequency. This is quite different from the example given above for radiative exchange. Note that we are not speaking of lattice vibrational frequencies but of radiation frequencies. We thus speak of two "coupled" oscillators. To further illustrate this concept, suppose we take two dipoles, there wUl be an electric moment, E 6), which is a vector product whose strength is a function of the angle, 6, between the vector moments of the dipoles ... 

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