Energy absorption, physical processes

By absorption of light a molecule is promoted to a higher electronic state. The monomolecular physical processes for the dissipation of the excess energy are outlined in Fig. 5 in a so called Jablonski diagramm. In principle one has to differentiate between radiative and non-radiative deactivation on the one side and on the other side one has to consider if the multiplicity of the system is conserved or not. Radiative deactivation, i.e. deactivation accompanied by emission of light, is termed fluorescence if the transition occurs with spin conservation and phosphorescence, if spin inversion occurs. 

By far the most interesting application to date is the ability to crosslink polymers in the solid state, and much research has been devoted to studying the reactions involved. The initial physical process of energy absorption and the final chemical change—formation of crosslinks—can be readily determined. However, there is still considerable doubt as to the intermediate reactions, and this problem offers an appropriate start of this review. 

The physical processes by which natural gas liquids are recovered include phase separation, cooling, compression, absorption, adsorption, refrigeration, and any combination of these. Obviously the definition already stated excludes refinery light volatiles produced by the destructive decomposition of heavy petroleum fractions and it also excludes liquids that may be produced synthetically from natural gas. These distinctions are of economic importance in considering our basic energy reserves. Both the refinery volatiles and the synthetic liquids represent conversion products from other hydrocarbons and the conversion is usually attended by a considerable loss. Thus it has been stated that only about 47% (17) of the energy of natural gas is realized in the liquid hydrocarbon products of the Fischer-Tropsch type of synthesis. 

Hart and Boag s discovery (13) of the broad optical absorption band of the e aq in irradiated water confirmed the conclusion (7, 8) that the eaqy instead of the H atom, is the principal reducing intermediate in the bulk of the solution. Understandably, the Lea-Platzman (31) viewpoint of the primary physical processes of energy absorption gained currency over the Samuel-Magee (34) viewpoint. Their disagreement concerned the fate of the electron from primary ionization of water Platzman (31)... 

Existing physical absorption AGR processes are relatively energy inefficient for application in coal gasification they use substantial amounts of steam or stripping gas to regenerate lean solvent and power to pump lean solvent into the AGR absorber. In the treatment of crude gas with substantial carbon dioxide content, work available by expansion of separated carbon dioxide from its partial pressure in the crude gas, typically 100-300 psia, to atmospheric pressure, is not recovered. In theory, an AGR process could recover and utilize this potential energy. 

These reactions taking place in the RC are the primary chemical reactions of photosynthesis. (A detailed description ot these primary chemical reactions in RCs of purple bacteria is given in Chapter 3.) The primary physical processes of photosynthesis are light absorption and transfer of excitation energy. These processes take place mainly in the light-harvesting complexes (LHCs) described in Chapter 11. 

Recently there has been a lot of interest in energy migration in Gd compounds, because this opens interesting possibilities to obtain new, efficient luminescent materials (201,202). The Gd sublattice is sensitized and activated. The sensitizer efficiently absorbs ultraviolet radiation and transfers this to the Gd " " sublattice. By energy migration in this sublattice the activator is fed and emission results. Absorption and quantum efficiencies of over 90% have been attained. The physical processes can be schematically presented as follows ... 

The chemical/physical process common to all photoactivated toxicity events is the absorption of photon energy (Figure 2A), generally in the 280 to 400 nm wavelength range, by a sensitizer molecule (e.g., PAH) [94,95]. The energy absorbed results in promotion of electrons from their ground-state orbitals to... 

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