The intensity of a HeNe laser light (633 nm), R, reflected off Pt(111) microfacets in 0.1 M H2SO4 was monitored as a function of potential, E, in the range 0.05 ≤ E ≤ 0.85 V vs. a reversible hydrogen electrode. As reported earlier for massive Pt(111) [Molina et al., J. Chim. Phys., 88, 1339 (1991)], R was found to vary monotonically with E within the potential region of the so-called "butterfly" peak. Plots of 1/R(∂R/∂E) vs. E calculated from the R(E) vs. E curves recorded both with massive Pt(111) and the facets yielded within the region of this peak a bell shaped curve similar to that reported for massive Pt(111) using modulated reflectance techniques [Huerta et al., J. Electroanal. Chem., 463, 109 (1999)]. A more quantitative analysis of the results obtained in this work revealed a striking similarity between that bell-shape curve and the "butterfly" peak.
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