Energy transfer mechanism, during

Chemiluminescence also occurs during electrolysis of mixtures of DPACI2 99 and rubrene or perylene In the case of rubrene the chemiluminescence matches the fluorescence of the latter at the reduction potential of rubrene radical anion formation ( — 1.4 V) at —1.9 V, the reduction potential of DPA radical anion, a mixed emission is observed consisting of rubrene and DPA fluorescence. Similar results were obtained with the dibromide 100 and DPA and/or rubrene. An energy-transfer mechanism from excited DPA to rubrene could not be detected under the reaction conditions (see also 154>). There seems to be no explanation yet as to why, in mixtures of halides like DPACI2 and aromatic hydrocarbons, electrogenerated chemiluminescence always stems from that hydrocarbon which is most easily reduced. A great number of aryl and alkyl halides is reported to exhibit this type of rather efficient chemiluminescence 155>. 

During the falling rate phase of drying, models based on rate-limiting diffusion within the particles and also from external vapor diffusion on the particles have been proposed, but the primary energy transfer mechanisms remain the same. 

For more than three decades, van der Waals (vdW) complexes have become prototypes for studying energy transfer mechanisms and weak intermolecular forces. During these years, the understanding of vdW forces has expanded dramatically. With the development of experimental techniques such as supersonic nozzle expansion, and by performing more accurate ab initio electronic structure calculations, it became possible to study the structure and dynamics of vdW complexes in more detail. 

Kepler carried out fluorescence quenching studies and concluded that the migration of the exiton is the most probable energy transfer mechanism of poly(vinyl carbazole). He, furthermore, suggested that the exiton can visit one thousand monomer units during its lifetime. This is a distance of about... 

The formation of activated species during mechanoehemieal degradation is, in general, not sufficiently documented both experimentally and with respect to the proposed mechanisms to give a definite proof of their existence. In the dilute state, the rate of energy transfer is high and it is reasonable to assume that any activated species, if present, will be thermalized well before the occurrence of a chemical reaction. 

Hydrazide chemiluminescence has been investigated very intensively during recent years (for reviews, see 1>, p. 63, 2>, 90>). Main topics in this field are synthesis of highly chemiluminescent cyclic diacyl hydrazides derived from aromatic hydrocarbons, relations between chemiluminescence quantum yield and fluorescence efficiency of the dicarboxylates produced in the reaction, studies concerning the mechanism of luminol type chemiluminescence, and energy-transfer problems. 

Figure 6. A plot of the free energy contribution arising from the protein surroundings as a function of H04...N5 distance during the proton transfer mechanism.

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