Cyclic voltammetric experiments triggered by a laser pulse permitted rapid-scan (1000-3000 V s-1) voltammograms to be obtained at various times (0.01 s to 30 min) after laser activation of carbon fiber electrodes. A heterogeneous electron transfer rate constant k-degrees of 0.90 +/- 0.05 cm s-1 was observed for Ru(NH3)62+/3+ at a laser-activated carbon fiber disk electrode of diameter 00 mum. This value was constant with time after laser activation for about 10 s but decayed by approximately 70% over a 20-30 min period. Laser exposure did not cause activation in O2-saturated electrolyte, and brief electrochemical oxidation rapidly decreased the observed rate constant. The results indicate inhibition of Ru(NH3)62+/3+ electron transfer by a neutral surface oxide layer. A model for the decay of k-degrees after laser activation based on first-order formation of a neutral oxide layer is proposed.