Square-wave voltammetry of dissolved redox couple

A theory is developed of square-wave voltammetry of the system in which both the reactant and the product of a simple electrode reaction are initially present in the electrolytic solution. A net response of fast and reversible electrode reaction depends on the sum of concentrations of reactant and product. Under this condition the ratio of maxima and minima of the components of net response can be used for the calculation of the ratio of concentrations of reactant and product. If the electrode reaction is kinetically controlled, the net response may split in two peaks. The potentials of these peaks can be used for the determination of transfer coefficients.     

Theory of reverse scan square-wave voltammetry influenced by the kinetics of reactant adsorption

A model of electrode reaction complicated by slow adsorption of the reactant is developed for square-wave voltammetry with inverse scan direction. The relationship between the dimensionless net peak current and the logarithm of dimensionless rate constant of adsorption is a curve with a minimum and a maximum. For this reason the ratio of real net peak current and the square-root of frequency is a non-linear function of the logarithm of frequency and exhibits either a maximum or a minimum. The frequency of extreme serves for the estimation of the rate constant: log(k _ads /D ^1/2 ) = log(k* _ads )_crit + 0.5 log f _crit , where (k* _ads ) _crit is a critical dimensionless rate constant of adsorption. Square-wave voltammetry is sensitive to the kinetics of adsorption if k _ads < 10² cm s⁻¹      

Bright soliton interactions in a $$\mathbf (2 +\mathbf 1) $$ ( 2 + 1 ) -dimensional fourth-order variable-coefficient nonlinear Schrödinger equation for the Heisenberg ferromagnetic spin chain

Nonlinear Dynamics - Interactions of bright solitons in the Heisenberg ferromagnetic spin chain, governed by a $$(2+1)$$ -dimensional nonlinear Schrödinger equation with variable coefficients,...     

Quasi-stable propagation of vortices and soliton clusters in saturable Kerr media with square-root nonlinearity

Analytical and numerical investigation of the propagation of optical beams in Kerr-like saturable photorefractive media is carried out, utilizing a novel model for the local isotropic part of the space-charge field generated in the medium. Using a variational technique, optimal propagation parameters for the most stable propagation of otherwise unstable single Gaussian, single vortex, and optical soliton cluster beams are determined. Analogy between a ring of identical weakly overlapping solitons and a vortex of the same topological charge is explored.     

Dynamic instability of self-induced bidirectional waveguides in photorefractive media

We report on the experimental observation of a dynamic instability in the interaction of counterpropagating self-trapped beams in a photorefractive strontium barium niobate crystal. While the interaction of copropagating spatial optical solitons exhibits only transient dynamics, resulting in a final steady state, the counterpropagating geometry supports a dynamic instability mediated by intrinsic feedback. Experimental observations are compared with and found to be in qualitative agreement with numerical simulations.     

Theory of square-wave stripping voltammetry with adsorptive accumulation

Summary A model of the anion-induced adsorptive accumulation combined with a square-wave voltammetric stripping is developed. The dependence of peak currents and peak potentials on the reversibility of redox reactions and on the reaction mechanism is demonstrated. The sensitivity of the method is estimated.

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Theorie der Square-Wave Stripping Voltammetrie mit adsorptiver Anreicherung

     

Collisions of Two Spatial Solitons in Inhomogeneous Nonlinear Media

Collisions of spatial solitons occurring in the nonlinear Schröinger equation with harmonic potential are studied, using conservation laws and the split-step Fourier method. We find an analytical solution for the separation distance between the spatial solitons in an inhomogeneous nonlinear medium when the light beam is self-trapped in the transverse dimension. In the self-focusing nonlinear media the spatial solitons can be transmitted stably, and the interaction between spatial solitons is enhanced due to the linear focusing effect (and also diminished for the linear defocusing effect). In the self-defocusing nonlinear media, in the absence of self-trapping or in the presence of linear self-defocusing, no transmission of stable spatial solitons is possible. However, in such media the linear focusing effect can be exactly compensated, and the spatial solitons can propagate through.     

Valley Hall edge solitons in honeycomb lattice with an armchair-type domain wall

Nonlinear Dynamics - Thanks to the topological protection, photonic topological edge states can move along the edges of photonic crystals without radiating into the bulk or reflecting when...     

Bright and dark solitons in optical metamaterials

This paper addresses the dynamics of solitons in optical metamaterials. Both bright and dark soliton solutions are obtained. The ansatz method of integration is employed to extract the 1-soliton solutions to the governing equations. A couple of constraint relations are obtained in order for these solitons to exist. A few numerical simulations are also given to expose the dissipative effects.