Exchange mechanism of energy

C3.4.6 EXCHANGE MECHANISM OF ENERGY TRANSFER IN FORBIDDEN TRANSITIONS... 

This formula was first derived in ref. 6 when calculating the kinetics of donor luminescence decay in the presence of the randomly, i.e. chaotically, located acceptors under the condition n N and on the assumption of the resonance exchange mechanism of energy transfer. Similar equations were later used for the analysis of experimental data on the kinetics of electron tunneling reactions obtained under conditions of the chaotic distribution of the reagents and at n < N. As a rule, only the first term of the exponent in eqn. (23) has been taken into account, which is equivalent to employing the previously mentioned (see Sect. 2.1) stepwise approximation of the function 0(R,t) = exp[- 1V(jR)(]. In this case, one obtains... 

It is worth noting that while Dexter s name became synonymous with the exchange mechanism of energy transfer, the main body of his seminal paper is devoted to spin-allowed EET mediated by the various multipole terms of the Coulomb interaction. 

The Dexter or electron exchange mechanism of energy transfer. 

Fig. 4.14. Schematic representation of the (A) Coulombic and (B) exchange mechanisms of excitation energy transfer. Cl Coulombic interaction EE electron exchange.

The interchange character of the water-exchange mechanism of the studied seven-coordinate complexes can be a reason why there is no clear correlation between their rates for the exchange process and the energies required for the dissociation of the coordinated water molecule. AE is also not possible to correlate with the catalytic rate constants published in the literature. 

Figure 3.36 The Dexter mechanism of energy transfer through simultaneous electron exchange.

The observed angular-dependent shifts at the various collision energies are well described by (11.77). From the observed shifts the physically interesting quantity s/b can be determined by (11.77), which indicates the average location in the quasimolecule where the electron is ejected. It is found that s/b is always close to unity, which means that the electron comes from the helium. This is very direct evidence of the exchange mechanism of Pgl [see equation (11.69)]. 

On cooling films of pure polystyrene to 77K the ratio Ie/Im goes to almost zero (14). Assuming that excimer traps are preformed in the TTlm when cast, the population of such traps will remain constant, once the film is formed. Neither the exchange nor the dipole-dipole mechanism of energy transfer is particularly sensitive to temperature and thus it is difficult to see why the traps should not be populated at very low temperatures, if indeed the mechanism of population is by e.e.m. into the traps. 

While several hours (e.g., 7h) are required for conventional LIBs with a graphite anode and a LiFeP04 cathode for the completion of the necessary intercalation processes in one of the electrodes and deintercalation in the other electrode, the time of ion migration in lithium-cation-exchange capacitors is several minutes. Further studies are required for a more clear determination of the main mechanisms of energy storage in such PsCs. 

A new field of chemistry was opened, namely the chemistry of labile particles atoms, free radicals, radical ions, carbenes, etc. The fest development of experimental techniques suitable for monitoring fast and ultrafast processes led to the study of mechanisms of energy exchange in collisions of particles and initiated the formation of nonstationary kinetics. 

Recently we have found a type of tightly bound ATP which exists even in the presence of saturating concentrations of hexokinase (Aflalo, Shavit, 1982) but is exchangeable with exogenous ATP. This bound ATP appears to arise from a free species of ATP sequestered near the active site during photophosphorylation. The slowed down diffusion of the newly made ATP to the outer medium space allows its binding to proximal non-catalytic sites. Thus, mass transfer of nucleotides between the active site and the bulk medium may limit the steady state rate of ATP synthesis and should be considered in proposals on the mechanism of energy transduction. 

Thennal equilibrium means free transfer (exchange) of energy in the fonn of heat, mechanical (liydrostatic) equilibrium means free transfer of energy in the fonn of pressure-volume work, and material equilibrium means free transfer... 

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