Electron excitation, transfer

Lee, J., Wang, Y., and Gibson, B. G. (1991a). Electronic excitation transfer in the complex of lumazine protein with bacterial bioluminescence intermediates. Biochemistry 30 6825-6835. 

Similar to molybdenum oxide catalyst the capability to emit singlet oxygen is inherent to Si02 doped by Cr ions as well. Similar to the case of vanadium oxide catalysts in this system the photogeneration occurs due to the triplet-triplet electron excitation transfer from a charge transfer complex to adsorbed oxygen. 

The cross-section of light absorption in processes (71) and (73) can be calculated according to eqns. (68) and (69), assuming d to be the dipole matrix element between the states A and A or B and B. The rate constants of processes (72) and (74) can be calculated with the help of the equations presented in the previous sections of this chapter. The rate constant of process (75) can be calculated using the formula which is the same as the well-known Forster-Dexter formula for electron excitation transfer [30],... 

ELECTRONIC EXCITATION TRANSFER BETWEEN INERT GAS ATOMS... 

Determination of macromolecules conformations is one of the basic problems of science about polymers. Simultaneously with development of theory [4-6] the perfection and enrichment of experimental methods of determination of macromolecules conformations in various phase and aggregate states occurs. However the method of neutron scattering was almost the only one method allowing reliable determination of polymer chains conformation in solid amorphous state until now [7], Not long ago they begun to use with this aim also the method based on measurement of rate of electron excitement transfer between molecules of chromophores covalent bonded with polymer chain [8],... 

Intramolecular proton transfer in electronically excited transfer in, say, salicylic acid ester and other aromatic compounds leads to deexcitation of the energized electron [43-45]. In photoreduction processes, electron transfer often precedes proton transfer [46] the stability of the protonic bond is at least partially due to an n-a interaction [47]. The strength of the protonic interaction appears to be proportional to the ionization potential of the donor and is sensitive to solvent polarity [48]. These effects have hardly been touched on in biologically important transitions and represent an important new field of research. 

I. Yamazaki, N. Tamai, T. Yamazaki, Electronic Excitation Transfer in Organized Molecular Assemblies , J. Phys. Chem., 94,516 (1990)... 

Relationship between Electron and Electronic Excitation Transfer... 

In the following paragraphs we will briefly discuss the mechanisms of electronic excitation transfer most frequently encountered in molecular systems, and outline the formalism most commonly used to interpret energy-transfer data. More attention will be devoted to the exchange-mediated excitation transfer processes because of their particularly close relationship to charge transfer. 

The first improved theory addressing the weakly coupled, or non-adiabatic electronic excitation transfer was the semiclassical vector model proposed by Forster [15]. It was further developed and refined by Levinson [16], Kasha [17], and others [18], who sometimes referred to it as the molecular exciton theory . Notably, this was the first successful attempt to link the rate of electronic excitation transfer with readily available experimental parameters, such as the absorption spectrum of the... 

While at first it might seem counterintuitive, this effect is readily explained in terms of the simplest zero-order orbital picture of the electron and electronic excitation transfer processes. Triplet transfer to and from a typical closed-shell organic molecule involves a change in occupancy of both the HOMO and LUMO orbitals of the donor and the acceptor. For an olefinic or aromatic donor or acceptor, this can be represented as ti tc —> (donor) and n n (acceptor). This... 

All the necessary excited-state parameters (frequencies, force constants, and equilibrium geometries) can be obtained from MO calculations or, in a few cases, from excited-state Raman measurements. The above rate expression, like the standard Marcus-Jortner equation, can be readily modified to include more than one vibrational mode. The difference between the two approximations should be most pronounced when h v — vpj > ksT and /i ri — vp > Aj. The second condition is more likely to be satisfied for electronic excitation transfer than for charge transfer. 

One of the basic mechanisms in multichromophoric systems, electronic excitation transfer has been in the past and still is in many studies largely described using Forster theory. As stated by Forster [20], this model is developed for the weak coupling limit as it is based on an equilibrium Fermi Golden Rule... 

A microscopic fluorescence spectrum is potentially very informative, since it reflects stoichiometric ratios, efficiencies of electronic excitation transfers among the pigment-protein complexes, and quenching mechanisms inherent in the photo synthetic reactions. Since the multiple fluorescence bands are overlapping, spectral detection based on a polychromator and multichannel detector is more informative than detection using a few channels based on dichroic mirrors and band-pass filters. 

On the basis of above mentioned it may be assumed that effect of light stabilization is probably linked with the increase of electronic excitation transfer from polymer to PAC. And it may be expected that the more complex is PAC molecule the more vibrating degrees of freedom it has and the more is the observed effect of excitation suppression [180]. 

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