Symmetric Periodic Potential Research Articles

Adsorption and electrooxidation of ethylene on Au surfaces

The electrochemical behavior of ethylene electrooxidation on preferentially oriented Au surfaces is investigated in 1 M H2 SO4 aqueous solution at 25°C. A symmetric square wave periodic potential signal is applied to polycrystalline Au electrodes to obtain (111)-, (110)-, and (100)-type oriented surfaces, which are characterized by cyclic voltammograms and SEM micrographs. It is found that ethylene adsorbs at potentials just below the potential of zero charge of the Au/1 M H2 SO4 interface, and two residues are detected in an anodic stripping experiment. The adsorbed ethylene voltammetric electrooxidation, and the bulk ethylene anodic polarization curves are measured at the differently oriented Au surfaces.

Effects of multiplicative noise on fluctuation-induced transport

We study the transport of a Brownian particle moving in a ratchet-like periodic potential driven by multiplicative colored noise, and an analytic expression for the steady current with weak noise-strength is obtained. The results show that the effect of the multiplicative noise is equivalent to additive noise acting on a particle moving in an effective potential with a slope modified from the original one. Then a net steady current may arise even in the cases of white noise and a symmetric periodic potential. Some simple models are studied and discussed.

Synchronized first-passages in a double-well system driven by an asymmetric periodic field

We perform a Langevin dynamic numerical simulation of a double-well potential system subjected to an asymmetric sawtooth type external time varying field and white noise forces. The hysteresis loss calculated from the first-passage time distribution obtained shows an asymmetric behaviour with respect to the asymmetry in the field sweep. The hysteresis loss in our model being a measure of the synchronized passages from one well to the other, indicates asymmetric “correlated” passages in the two opposing directions when driven by a temporally asymmetric external field in the presence of white noise (fluctuating) forces. The implication of our results for the phenomenon of a predominantly unidirectional motion of a Brownian particle in a symmetric periodic (non-ratchet-like) potential is discussed.