Reactions coherence

For a fuller description, see the scheme shown in the next page reflecting all known types of synchronous reaction coherence. 

As follows from the data shown, the phenomenon of synchronous reaction coherence promotes a growth of interest in selective oxidation processes with hydrogen peroxide. This direction becomes a prime importance for modem investigations. 

It is hoped that the efforts to lay a foundation for future process design, which may change the direction of applied chemistry in many branches, will be useful. Therefore, one more question about the practical value of synchronous reaction coherence is raised in this book. 

However, the requirements for chemical synthesis and those for reaction dynamics studies are different. In chemical dynamics studies, we activate starting molecules at once and observe the subsequent reaction. Coherency of the activation is important but the number of activated molecules is not so important as long as we can observe them. In chemical synthesis, however, the number of molecules which participate in the reaction is much more important because it directly relates to productivity. Therefore, all the molecules in the system should be activated, but coherency of the activation is less important. We usually synthesize compounds on the 10 " -10°mol scale in laboratories and on the 10 -10 mol scale in chemical plants. Such amounts of molecules should be activated in a very short period for time-efficient chemical synthesis. 

Electron Transfer Reactions Coherent Control OF Chemical Reactions Lasers, Ultrafast Pulse ItecHNOLOGY Luminescence Molecular Beam Epitaxy, Semiconductors Nanostructured Materials, Chemistry of Noni.inf.ar Optical Processes... 

Tannor D J and Rice S A 1988 Coherent pulse sequence control of product formation in chemical reactions Adv. Chem. Rhys. 70 441 -524... 

Tannor D J, Kosloff R and Rice S A 1986 Coherent pulse sequence induced control of selectivity of reactions exact quantum mechanical calculations J. Chem. Rhys. 85 5805-20, equations (1)-(6)... 

Shapiro M and Brumer P 1989 Coherent chemistry—Controlling chemical reactions with lasers Acc. Chem. Res. 22 407... 

Zhu I, Wdom A and Champion P M 1997 A multidimensional Landau-Zener description of chemical reaction dynamics and vibrational coherence J. Chem. Phys. 107 2859-71... 

Wynne K and Hochstrasser R M 1995 Anisotropy as an ultrafast probe of electronic coherence in degenerate systems exhibiting Raman scattering, fluorescence, transient absorption and chemical reactions J. Raman Spectrosc. 26 561-9... 

Zhu L, Sage J T and Champion P M 1994 Observation of coherent reaction dynamics in heme proteins Science 266 629-32... 

Vos M H, Jones M R, Hunter C N, Breton J and Martin J-L 1994 Coherent nuclear dynamics at room temperature in bacterial reaction centers Proc. Natl Acad. Sci. USA 91 12 701-5... 

Coherent anti-Stokes Raman spectroscopy (CARS) [59] has also found utility in the detemiination of the internal state distributions of products of chemical reactions. This is one of several coherent Raman spectroscopies based on the... 

Seideman T, Shapiro M and Brumer P 1989 Coherence chemistry—controlling chemical reactions with lasers Chem. Phys. 90 7132... 

Calculations within tire framework of a reaction coordinate degrees of freedom coupled to a batli of oscillators (solvent) suggest tliat coherent oscillations in the electronic-state populations of an electron-transfer reaction in a polar solvent can be induced by subjecting tire system to a sequence of monocliromatic laser pulses on tire picosecond time scale. The ability to tailor electron transfer by such light fields is an ongoing area of interest [511 (figure C3.2.14). 

The important issues are how energy is partitioned, tire degree of coherence in tire fonnation of tire product and whetlier tire reaction is adiabatic (solvent easily follows reactant motions) or nonadiabatic [8]. A nonadiabatic tlieory would be much more complicated. 

Reactions belonging to the same reaction type are projected into coherent areas on the Kohonen map this shows that the assignment of reaction types by a chemist is also perceived by the Kohonen network on the basis of the electronic descriptors. This attests to the power of this approach. 

Properties. SUica gel (see Eig. 8) is a coherent, rigid, continuous three-dimensional network of spherical particles of coUoidal sUica. Both sUoxane, —Si—O—Si—, and sUanol, —Si—O—H, bonds are present in the gel stmcture. The pores are intercoimected and fUled with water and/or alcohol from the hydrolysis and condensation reactions (40). A hydrogel is a gel in which the pores are filled with water. A xerogel is a gel from which the hquid medium... 

Descriptions of Physical Objects, Processes, or Abstract Concepts. Eor example, pumps can be described as devices that move fluids. They have input and output ports, need a source of energy, and may have mechanical components such as impellers or pistons. Similarly, the process of flow can be described as a coherent movement of a Hquid, gas, or coUections of soHd particles. Flow is characterized by direction and rate of movement (flow rate). An example of an abstract concept is chemical reaction, which can be described in terms of reactants and conditions. Descriptions such as these can be viewed as stmctured coUections of atomic facts about some common entity. In cases where the descriptions are known to be partial or incomplete, the representation scheme has to be able to express the associated uncertainty. 

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