Such anomalous behavior of j lim and α (or 1-α) indicates a departure from the Butler-Volmer model of electrochemical kinetics, which was used to analyze the data. In a predictive theoretical study, Feldberg showed that, under certain conditions, the steady-state voltammograms on disk ultramicroelectrodes deviate from the Butler-Volmer behavior and instead follow the Marcus-Hush theory. Crucially, the Butler-Volmer model continues to produce a good voltammetric fit but k 0 and α (or 1-α) become mere fitting parameters. Consequently, their apparent values increase and decrease, respectively, and the physical value of j lim decreases as Marcus-Hush behavior dominates, much in agreement with our observations. The qualitative conditions necessary to observe these anomalies were identified as: large potentials, small k 0 , small electrode size, and small λ, i.e. "fast" redox systems. Feldberg argued that such conditions are difficult to achieve simultaneously in an experiment, but fortuitously, our experimental system favorably meets all of these conditions. For λ = 1.0 eV, the two kinetics models are only distinguishable when |E -E 0' | ≥ 0.5 V (easily accessible in our system), and 99% of the Marcus-Hush potential-independent k 0 plateau is reached when |E -E 0' | ≥ 1.5 V. Furthermore, the following distinguishability condition must be met: