Line narrowing reaction mechanism

In order to explain all the salient features of the key experimental results on ECT (viz. listed as 1. to 6. at the beginning of Section II, Phenomenology of ECT), Vijh25 proposed a detailed electrochemical mechanism in which electroosmosis of the tissue (and thence water movement from anode to cathode) and electrode reactions (thence necrosis of the tissue, pH changes etc.) play the dominant roles. In particular, he presented a model and some quantitative considerations that delineate Nordenstrom s idea of electroosmosis through the narrow interstitial channels lined with fixed charges as the mechanism of the electrochemical destruction of the tumor tissue.10 Also he examined the role of electrode reactions and other events as possible contributory factors, as follows25 in Section III.2. 

For radicals in a liquid environment the excitation and relaxation processes are very fast, which results in a narrow line shape. However, in the solid state these processes are slower, which results in a much broader line shape. Spectra A and B are characteristic of very mobile radicals. These radicals are present in a concentration of about 10 f mol l 1, during the first 3 min of reaction. Spectrum E is characteristic of less-mobile radicals present in a solid environment. Similar spectra were obtained after this time. Then, it is inferred that at 6 min (macro)gelation takes place, which was confirmed by experiments performed with dynamic mechanical analysis. 

In summary it seems that in situ synthesis of long chain carbon molecules is presently the most convincing of the various formation mechanisms. In particular, spallation of organic grains s ms rather unlikely in the cold dark clouds such as TMC 1. We note, incidentally, that the dark clouds produce an absolutely clean chemistry , in the sense that many types of reactions which occur in terrestrial chemistry are excluded. Shocks, for example, appear not to be present if one can judge from the observed narrow line profiles. The gas is very quiescent and cold. On the other hand, ions such as HCO and (Guelin et al., 1977)... 

This is the naive picture on which many tentative models of chemical reactions used in the past were based. The material model is reduced to the minimal reacting system (A+B in the example presented above) and supplemented by a limited number of solvent molecules (S). Such material model may be studied in detail with quantum mechanical methods if A and B are of modest size, and the number of S molecules is kept within narrow limits. Some computational problems arise when the size of reactants increases, and these problems have been, and still are, the object of active research. This model is clearly unsatisfactory. It may be supplemented by a thermal bath which enables the description of energy fluxes from the microscopic to the outer medium, and vice versa, but this coupling is not sufficient to bring the model in line with chemical intuition and experimental evidence. 

This made it possible to identify surface hydroxyl groups in zeolites [4,5], characterize Brpnstead acidity [6], porosity, and adsorption sites with adsorbed probe molecules [7-13]. Later on, the adsorbed reaction products were characterized with MAS NMR [14], which provided a stimulus of application of MAS NMR to characterize the chemical reaction occurrence on zeolites [15] with the aim of unraveling the mechanisms of the reactions. Note, however, that researchers sometimes do not have to narrow the NMR signals with MAS to characterize the solids. For example, analysis of the line shape evolution with temperature for wide-line NMR spectra of adsorbates in zeolites affords a valuable information on the adsorbate molecular dynamics [16,17],... 

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