Dipole–dipole coupling effects upon infrared spectroscopy of compressed electrochemical adlayers: Application to the Pt(111)/CO system

作者：Mark W. Severson, Christopher Stuhlmann, Ignacio Villegas, Michael John Weaver · 发表于：The Journal of Chemical Physics · 年份：1995 · DOI：10.1063/1.469950 · 被引用次数：155 · 研究领域：Electrochemical Analysis and Applications、Spectroscopy and Quantum Chemical Studies、Molecular Junctions and Nanostructures

Experimental infrared spectra for CO adlayers on Pt(111) electrodes having known real-space structures as deduced by scanning tunneling microscopy are compared with predictions extracted from conventional dipole–dipole coupling models in order to test the validity of such treatments for compressed electrochemical adlayers, especially with regard to band-intensity transfer effects. The specific structures considered are (2×2)–3CO and (√19×√19)R23.4°–13CO hexagonal adlayers; the former is especially close packed (θCO=0.75) with a pair of threefold hollow and one atop CO per unit cell, while the latter has a lower coverage (θCO=13/19) and involves largely asymmetric binding sites. The comparisons between dipole-coupling theory and experiment include infrared spectra for various 13CO/12CO mixtures, thereby exploiting the well-known systematic alterations which are induced in the degree of coupling for a given adlayer. Consistent with an earlier assessment (Ref. ) the conventional dipole–dipole treatment can account semiquantitatively for the marked higher intensity of the atop relative to the threefold hollow C–O stretching band in the observed infrared spectra even though the occupancy on the latter site is twofold greater and the singleton frequencies are substantially (∼280 cm−1) different. This coupling-induced intensity transfer toward the higher-frequency band component is likely to be a widespread phenomenon for densely packed adlayers. For the (2×2) adlayer, however, the ...