Universal transmission coefficients

It is assumed that the composite catalytic reaction involves several elementary steps, e.g., adsorption, surface reaction, and desorption, which may individually be treated according to TTST, i.e., each step is assumed to possess its own transition state. For example, for the adsorption of A, the forward step is represented by, A + S [X ] - A S. The free energy changes of activation associated with each step may, of course, be substantially different providing justification of the common assumption of the rate determining step (rds). The rate of the forward elementary step i is proportional to the universal frequency, V = kgT jh [2], a transmission coefficient, K, varying between 0 and 1 [3], and the concentration of the transition-state complex (TSC)... 

Where k is the transmission coefficient, A(f is the difference in standard Gibb s free energy between the reactants and the transition state, Rg is the universal gas constant. Based on activated complex theory, the standard volume of activation (AE ) of a reaction is related to the pressure dependence of the reaction rate constant as expressed by. 

The rate of the chemical reaction A+B -> Products is equal to the number of activated complexes passing over the activation barrier each second, which is given by the concentration of activated complexes multiplied by the transmission coefficient v, a universal factor for all systems given by the relation... 

The rate constant is defined by equation (2), according to the Theory of Absolute Reaction Rates (67,83). In equation (2), k refers to the specific reaction rate, the equilibrium between the normal and activated states of the reactants, AF the free energy, AH the heat, AJB the eneigy, AT the volume change, and AS the entropy, all of activation, p the hydrostatic pressure, T the absolute temperature, and R the gas constant. The expression K kT/h) is the universal frequency for the decomposition of the activated complex in all chemical reactions. In this, k is the transmission coefficient, usually equal to 1, IT the absolute temperature, Jb the Boltzmann constant, and h Planck s constant. 

The main research activities using a FPA detector for FT-IR imaging began in 1997, since when the group of Koenig, at Case Western Reserve University in Cleveland, USA, has made important contributions to this research area. In their first FT-IR imaging applications in the transmission mode (1996, 1998, 1999), the group studied the diffusion of liquid crystals into polymers. The diffusion process was analyzed in detail and quantitative results, such as diffusion coefficients, were derived [2-4]. 

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