Electronic energy transfer process

Microanalysis of the three PET-4,4 -SD copolymer yarns for sulfur yielded concentrations in agreement with the theoretical values. Since the 4,4 -SD comonomer was definitely incorporated into the three copolymer yarns, the absorption and luminescence characteristics of the copolymers point towards a co-absorption process between 4,4 -SD and PET rather than an electronic energy transfer process. 

D. H. Metcalf, S. W. Snyder, J. N. Demas, andF. S. Richardson, Chiral discrimination in electronic energy-transfer processes between dissymmetric metal complexes in solutions, 1. Am. Chem. Soc. 112, 5681-5895(1990). 

Hirayama, F. Lipsky, S. Saturated Hydrocarbons as Donors in Electronic Energy Transfer Processes New York. In Organic Scintillators and Liquid Scintillation Counting Horrocks, D.L., Peng, C.-T., Eds. Academic Press, 1971 205 pp. 

A few remarks would be in order on the potentiality of metal-containing polymers as application-oriented materials. The major applications of these materials are in the following directions (a) electronic materials, anisotropic optical materials - active species in electronic energy-transfer processes of lasers... 

In any allowed electronic energy transfer process, the overall spin angular momentum of the system should not change. This statement is known as Wigner s spin conservation rule. The rule is applicable whether the transfer occurs between an excited atom or a molecule and another molecule in its ground state or in the excited state. In an electronic transition between the energy states of the same molecule also, spin is necessarily conserved. But the phenomenon is governed by rules for dipole-dipole interaction. 

Prior to the discussion of kinetic isotope effects in mercury photosensitization, it is instructive to review briefly the salient features of electronic energy transfer processes in those systems. 

Stilbene photochemistry continues to provide a mine of riches for the dedicated photochemist, in particular Hochstrasser, Fleming, and their groups. Metcalf et al. have described chiral discrimination in electronic energy transfer processes enantioselective excited state quenching occurs. A study of singlet electronic energy transfer from cyclohexane to benzene appears to require revision of the benzene fluorescence efficiency in cyclohexane to 0.26 0.02 (Johnston and Lipsky). 

One of the earliest condensed-phase TRIR measurements monitored the recombination of photodissociated CO from carboxymyoglobin on the millisecond timescale. Since then TRIR has frequently been applied to coordination compounds, to characterize reactive intermediates for the elucidation of reaction mechanisms and to study their excited states and electron/energy transfer processes. 

The kinetics of these electronic-energy transfer processes are thus deceptively similar to those of encounter-controlled bimolecular chemical reactions, and their rates are related to viscosity in the same way as those of difhisional collision processes in which kinetic energy only is transferred. The physical mechanisms, however, must be very different. Chemical reactions that occur at every encounter require only that the reactants come into close contact and remain so for a sufficient time. Electronic energy will be transferred during an encounter only if, in addition, it is allowed by the spin-momentum rules, i.e., if there is sufficient spin-orbital coupling between D and A for the exchange of electrons to occur... 

An electronic energy transfer process is the one-step transfer of electronic excitation energy from an excited donor molecule (D ) to an acceptor molecule (A) in separate molecules (intermolecular energy transfer) or in a different part of the same molecule (intramolecular energy transfer) [863,867, 1766, 1804, 2161, 2162, 2220]. 

Electronic energy transfer process may occur by the following mechanisms ... 

Electronic energy transfer process may also occur via formation of exciplexes. An exciplex (excited charge transfer complex) is a well defined complex which exists in electronically excited states. An exciplex is formed between an excited donor (D ) and/or an excited acceptor A ) and donor (D) molecules ... 

Time-resolved CPL spectroscopic experiments have been employed to study the stereoselectivity of electronic energy-transfer processes among optically active species [34, 40, 41]. 

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