摘要:

In many cases energy transfer occurs between the ions1–8and therefore its efficiency depends not only on the diffusion of ions but on the Coulomb interaction. Diffusion causes ions to draw nearer. Consequently the rate of energy transfer increases because this rate decreases with increasing distance between the sensitizer (S) and the activator (A). The presence of the Coulomb interaction leads to the redistribution of ions A near the ion S. As a function of a sign of ionic charge the concentration of A near the ion S will be more or less in comparison with the random concentration of these ions in solution. Since the Debye radius of shielding can be compared with the critical radius of energy transfer (Förster's radius) the Coulomb interaction between ions often causes considerable changes in the observed efficiency of energy transfer.

ISSN:0038-7010    

DOI:10.1080/00387017808067767

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

The effect of diffusion on long-range energy transfer by dipole-dipole interaction1,2from electronically excited donor molecules D* to (unexcited) acceptor molecules A may be important in solutions3–7and in molecular crystals7–11. In solutions usually diffusion of matter occurs (the molecules perform a random walk) whereas in molecular crystals an excitation (exciton) migrates. Exciton migration can often be described in terms of an effective exciton diffusion tensor which may be highly anisotropic12–17. Because of the restricted space only the time dependence of the donor fluorescence after δ-excitation will be given. The extension to general excitation forms and to the acceptor flouorescence is a straightforward matter18,19.

ISSN:0038-7010    

DOI:10.1080/00387017808067768

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Aerated benzene solutions containing anthracene together with one of the carotenoids, β-carotene, β-apo-8′-carotenal, ethyl β-apo-8′-carotenate and canthaxanthin were subjected to laser photolysis. Under these conditions oxygen quenching of triplet anthracene produces the excited singlet state of molecular oxygen O2* (1δg) which in turn transfers energy to the carotenoid thereby yielding its triplet state, the absorption of which was monitored thereby confirming electronic energy transfer as the mechanism of quenching of O2*(1δg) by these carotenoids and enabling the bimolecular quenching constansts which vary from 1.2 – 1.45 × 10101 mol−1s−1to be measured.

ISSN:0038-7010    

DOI:10.1080/00387017808067769

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

The intermolecular triplet-triplet (T–T) electron energy transfer discovered by Ermolayev and Terenin in solid solutions and adsorbates1,2was later observed in various aggregate states: in liquid solutions of organic compounds3, in crystals4and vapours5,6. It has become rather a precise and effective method which allows one to study the properties of excited states of molecules and processes proceeding with their participation7. The use of the T–T-transfer for studying paths of degradation of excitation electron energy made it possible to considerably advance the problem of radiationless transitions in molecules8. Although the process of the T–T-energy transfer in all the media is conditioned by the exchange-resonance interactions9, its kinetics is different depending on the aggregate state. This paper deals with the regularities of the T–T-energy transfer in gas phase systems.

ISSN:0038-7010    

DOI:10.1080/00387017808067770

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

The energy transfer from the upper triplet states of diphenylamine, naphthalene and triphenylene to toluene and hexene-1 is studed. Two mechanisms of dissipation transferred energy in solvents are discussed.

ISSN:0038-7010    

DOI:10.1080/00387017808067771

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

The investigation of concentration effects in the solutions of luminescent compounds allows us to obtain the detailed information concerning interactions between molecules of dissolved substance. The increasing concentration of dye and pigment solutions is known to lead to the concentration depolarization phenomena (CDF) and the concentration quenching of fluorescence (CQF). At present the overall of these phenomena is rather widely investigated both in theoretical and experimental aspects. Nevertheless the problem of the mutual relation of the concentration depolarization and the concentration fluorescence quenching remains yet unsolved. The improvment of the CDF theory, undertaken in last years, as well the using new methods of investigation, give the real possibility to carry out the comparison of theory and experiment more strictly.

ISSN:0038-7010    

DOI:10.1080/00387017808067772

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

In photosynthesis, only a small part of the pigment molecules (less than 1%) is directly involved in the primary photochemical reactions. These specialized molecules are located in definite centers (reaction centers: RC). The other pigment molecules form an antenna which first collects the light energy and then distributes the singlet excitation energy to the RC's. A RC and its (by relation of vicinity) associated part of the antenna are called a “photosynthetic unit” (PSU). The concept of PSU was born after the experiments of Emerson and Arnold1and has been developed in the thirties2–3. Franck and Teller4were the first to introduce in photosynthesis the concept of exciton migration. From that time an important theoretical work has been devoted to the problem of energy transfer in photosynthesis (see the review of Knox5). In this field the goal of the theoretician is to establish the master equation that governs teh excitation motion. The structural parameters of this equation have an important part from the biological point of view. As a matter of fact the collection antenna exhibits a short and a long distance degree of order. This spatial organization conditions the distribution of excitation energy to the Rc's. Consequently the study of energy transfer is inseparable from a structural analysis of the primary photochemical apparatus. In the following we will linit the discussion to the problem of gree plants.

ISSN:0038-7010    

DOI:10.1080/00387017808067773

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

The bimolecular quenching of an excited state molecule in fluid solution can occur in three fundamental ways:1–3(i) chemical reaction between the excited state and the quencher, (ii) electronic energy transfer from the excited state to the quencher, or (iii) deactivation of the excited state by some catalytic action of the quencher. The intimate nature of the quenching mechanism is often difficult to elucidate for a single excited state-quencher couple. More useful information can generally be obtained from correlations of data concerning homogeneous families of excited states and/or quenchers.

ISSN:0038-7010    

DOI:10.1080/00387017808067774

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Radiationless energy transfer between rare-earth ions (Ln3+) in solutions has some features: 1) the electronic transitions in Ln3+complexes causing the luminescence of energy donor and the absorption of energy acceptors are forbidden by Laporte's rule and are weakly intensive. Therefore the critical radius (Ro) of energy transfer between the rare-earth ions for dipole-dipole mechanism is close to that for exchange-resonant mechanism. This fact presents difficulties for unequivocal interpretation of the energy transfer mechanism. 2) The plus-three lanthanide ions exist in solution as a set of complexes with different number of charged ligands in the inner coordination sphere and hence with different total charge of complexes.

ISSN:0038-7010    

DOI:10.1080/00387017808067775

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Nonradiative electronic energy transfer (ET) is of great importance and of wide use in studies of chemiluminescence (CL) in solution. Some components of a chemiluminescent system, e. g. reactants, intermediates or products may serve as efficient energy acceptors. In some cases fluorescent energy acceptors, the activators of CL, are necessary components of a CL system. In contrast to the conventional (non-laser) photoexcitation the chemical excitation may produce a triplet state directly, rather than only via the excited singlet state.

ISSN:0038-7010    

DOI:10.1080/00387017808067776

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor