Quantitation of Molecular Orientation

In the spectroelectrochemical experiment, the simulation of reflectivity responses can become quite complicated owing to the multiple interfaces and phases through which the optical beam must pass [104]. However, the models employed have gained in sophistication over the years as they have been needed to assist in the design of cells and optical systems and in the interpretation of spectra [23, 80, 104, 189-193]. An expanded discussion of the computational approach and its application to a four-phase model of the infrared spectroelectrochemical experiment was presented by Pettinger and coworkers recently [104]. An example of its use and the type of detailed structural information that can be gained is described for the case of pyridine adsorption on an Au electrode [103]. 

The vibrational modes detected for adsorbed pyridine are of Oi symmetry. The inset to Fig. 7.12 shows that the transition dipole moments are directed along 

The relative intensities of the upward and downward bands in the in-situ infrared spectrum in Fig. 7.12 can be interpreted by considering general relationships that govern band intensity and infrared absorption strength. Equation 

The present chapter aims to highlight recent applications of these approaches in the study of adsorption and catalysis at weU-defined electrode surfaces and to describe related areas where important developments are occurring. Infrared spectroscopy continues to be widely used as a probe of CO surface electrochemistry, both when CO is the starting reactant and when it is formed as an intermediate. Investigations involving CO electrochemistry are targeting bimetallic 

Support from the U.S. National Science Foundation for the author s work in the area of infrared spectroelectrochemistry is gratefully acknowledged. 

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