| Abstract
| - The effect of 355 nm, 10 ns laser pulses of 3−11 MW cm-2 intensity on gold macrodisk electrodes has beeninvestigated. Repetitive pulsing increases the standard heterogeneous electron transfer rate constant, k°, forFe(CN)63-/4- from (9.2 ± 0.3) × 10-5 to (2.4 ± 0.1) × 10-3 cm s-1. The k° value becomes larger withincreasing laser pulse intensity, and the enhancement is removed by conventional mechanical polishing. Theeffect of laser irradiation on the electrode surface has been investigated using scanning electron microscopyand by measuring the capacitance as well as the open circuit potential. These results suggest that the primaryactivation mechanism involves thermally driven desorption of adventitious surface impurities. The dependenceof the laser-induced current−time transients on the applied potential has also been investigated. These transientsdo not exhibit the single exponential decay behavior expected if the laser pulse caused a simple change in theinterfacial potential, e.g., through changes in the interfacial ion distribution. Rather, they are interpreted interms of double layer charging at short times in response to a laser-induced change in the interfacial potentialfollowed by a thermal diffusion process that depends on the applied potential. While the resistance isindependent of the applied potential, the double layer capacitance of this interface that has been heated bythe laser pulse to approximately 500 K shows a minimum at +0.100 V that is consistent with the potentialof zero charge. The thermal conductivity and heat capacity depend strongly on the applied potential reachingmaximum values at approximately +0.100 V of 3.19 J cm-1 K-1 and 0.13 J g-1 K-1, respectively. The lowervalues observed at more extreme potentials are consistent with laser-induced heating of the interface andprovide a powerful new insight into the potential dependence of heat conduction in metals.
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