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For diffusion-limited reversible A+A⇋B reactions we reexamine two fundamental concepts of classical chemical kinetics—the notion of “chemical equilibrium” and the “law of mass action.” We consider a general model with distance-dependent reaction rates, such that any pair of A particles, performing standard random walks on sites of a d-dimensional lattice and being at a distance μ apart of each other at time moment t, may associate forming a B particle at the rate k+(μ). In turn, any randomly moving B particle may spontaneously dissociate at the rate k-(λ) into a geminate pair of As “born” at a distance λ apart of each other. Within a formally exact approach based on Gardiner’s Poisson representation method we show that the asymptotic t=∞ state attained by such diffusion-limited reactions is generally not a true thermodynamic equilibrium, but rather a nonequilibrium steady state, and that the law of mass action is invalid. The classical concepts hold only in case when the ratio k+(μ)/k-(μ) does not depend on μ for any μ. [ABSTRACT FROM AUTHOR]

In the present paper we analyze the kinetics of irreversible A+B→0 reactions in situations appropriate to electrolyte solutions. We consider diffusing species which experience short-range repulsive (attractive) interactions between like (unlike) particles and we highlight the role of fluctuations in the particles’ spatial distributions. We focus mainly on one-dimensional systems and devise a many-particle description of the reaction kinetics. In terms of our analytical approach we show that at intermediate times the interplay between fluctuations and short-ranged interactions gives rise to unusual behaviors, characterized by novel dynamical exponents of the particles’ mean concentrations. For batch reactions at longer times, when the concentrations drop off significantly, the usual fluctuation-induced behavior is recovered. We also analyze systems with external, steady sources of particles and we show that in such situations the effects of the interactions become decisive at long times. Our analytical findings are in good agreement with the results of numerical simulations, which we also present. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We study the direct incoherent energy transfer in systems, in which the molecules involved in the transfer process are attached to ideal (Gaussian) polymers, randomly arranged in a viscous solvent. In what the molecules’ attachment to polymers is concerned we consider two different situations: (a) each polymer chain contains at its opposite ends a donor and an acceptor molecule, (b) the donor molecules are dispersed randomly in the solvent and all acceptors are attached to polymers. In both cases we derive the donors’ decay forms exactly. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

In this work we report first analytical results on the dynamics and conformational properties of polyampholytes (PAs, polymers containing positive and negative charges) in the presence of external electrical fields. In terms of the Rouse model of polymer dynamics and in the so-called weak coupling limit we obtain for PAs explicitly the mean-square displacement both of the center of mass and of individual beads, and also determine the PAs’ equilibrium end-to-end distance. For a singly charged PA we also relate the findings to a fractional differential equation. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We discuss the influence of transport limitations on the kinetics of homopolymerization reactions. We show that in the systems in which the polymer’s diffusivity decreases faster than the first inverse power of its radius of gyration, the transport limitations represent the rate-controlling step and induce anomalous behavior of the characteristics of the process. For such systems we compute the evolution of the molecular weight distribution and its zeroth moment explicitly. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Examines the kinetic conditions of bimolecular based on catalytically activated reactions (CAR). Identification of elementary reaction act between reactants; Association between CAR and Collins Kimball type idea; Discussion on the characteristics of the catalytic site.