Low temperatures, chemical reactions

The intensely developing technique of high-resolution IR-spectroscopy of dimers composed of two different molecules in supersonic cooled jets offers a new promising approach to the quantum dynamics of reaction complexes. In essence, this is a unique possibility of modelling low-temperature chemical reactions. 

The effects of transfer of atoms by tunneling may play an essential role in a number of phenomena involving the transfer of atoms and atomic groups in the condensed phase. One may expect that these effects may exist not only in the proton transfer reactions considered above but also in such processes as the diffusion of hydrogen atoms and other light ions (e.g., Li+) in liquids, tunnel inversion and isomerization in some molecules, quantum diffusion of defects and light atoms in the electrode at cathodic incorporation of the ions, ion transfer across the liquid/solid interface, and low-temperature chemical reactions. 

The problems discussed here are closely related to the problem of calculating the rates at which a particle leaves a potential well and which govern the rates of chemical reactions. The most consistent description of low-temperature chemical reactions that included tunnelling and dissipation processes was given in Ref. 161. We shall be interested only in the thermally activated contribution which dominates for many systems at not too low temperatures. 

The points discussed in this appendix are of direct relevance to a description of the chemical reactions that involve surmounting the potential barrier. The barrier is surmounted due to thermal activation at high temperatures and due to tunneling at low temperatures, the latter fact accounting for an occurrence of low-temperature chemical reactions.216,217... 

It is well established that hydrogen forms more than one covalenl binary compound with carbon. Fluorine behaves similarly. Thus, fluorine forms CFi. C>F4. CjFV,. C.rFx and many higher hontologs. as well as the definitely imerstiiial compound (CF) . The other halogens form some similar compounds, although 10 more limited extent, and various polyhalogen compounds have been prepared. They exhibit the maximum covalencv of four and are therefore inert to hydrolysis and most other low temperature chemical reactions. 

There have been numerous studies of low-temperature chemical reactions of matrix-isolated reactants (see, for example, the review by Perutz [1985]). Two of the most interesting from the standpoint of this volume are the reactions of NO with 02 and 03 studied by Smith and Guillory [1977] and Lucas and Pimentel [1979]. The cis dimer (NO)2 has been formed in solid oxygen at 13-29 K. Reaction of this species with the 02 matrix forms the product N204 in an electronically excited state. The transition state structure is reportedly of the form... 

AUTOWAVE MODES OF CONVERSION IN LOW-TEMPERATURE CHEMICAL REACTIONS IN SOLIDS... 

Passing over to the computation of the rate constants of specific reactions, we again emphasize that the J(R) expansion from (37) in a power series of R is not necessary. It only enables one to obtain analyzable relations through application of different models of a solid. In the general case the problem of the calculation of low-temperature chemical reaction rate constants requires consecutive solution of two problems search of convenient PESs and averaging of the imaginary part of the action along the optimal path from relation (49). 

As in the description of low-temperature chemical reactions, these difficulties can be overcome by accounting for the barrier fluctuations in the... 

Benderskii, V., Goldanskii, V. and Makarov, D. (1991). Low-temperature chemical reactions. Effect of symmetrically coupled vibrations in collinear exchange reactions. Chem. Phys. 154, 407-424... 

Zhang, H., Du, N., Chen, B., Li, D. and Yang, D. (2009) Carbon nanotube-ZnO nanosphere heterostructures low-temperature chemical reaction synthesis, photoluminescence, and their application for room temperature NH3 gas sensor , Sci. Adv. Mater., 1,13-7. 

Du N, Zhang H, Chen B, Wu J, Li D, Yang D (2007) Low temperature chemical reaction synthesis of single-crystalline Eu(OH)3 nanorods and their thermal conversion to EU2O3. Nanotechnology 18 065605... 

Studies of low-temperature chemical reactions in the presence of external fields may elucidate several fundamental questions of modern chemical physics. As... 

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