Electroreflectance Spectroscopy ERS

Thus a complete description of the system under study has to take into account properties of these three phases. Optical properties of the interphase can be obtained from measurements of the reflectivity as a function of wavelength with systems showing no pronounced interphase, the optical properties of the metal can be studied. 

Initially, this method was called the electrolyte electro reflectance (EER) technique. 

The spectral range accessible for measurements is limited by the transmission properties of the electrolyte solution and the optical components, the intensity distribution of the used light source and the spectral sensitivity of the detector to values of about 220 X 1400 nm. 

The optical properties of a Au(lOO) surface in its reconstructed state differ markedly because of the participation of electronic surface states in the optical excitation these states depend on the crystallographic surface structure [95]. Surface band structure calculations have revealed the existence of empty surface states [96]. These surface states can be shifted in their energy by the electrode potential (Stark shift) [97]. Optical transitions into these states thus become potential dependent. 

In Fig. 5.16 the electroreflectance spectrum of the Au(100)-(1 x 1) surface shows two derivative-like features around 3 and 4.2 eV assigned to transitions from the bulk d-band into the aforementioned unoccupied surface states [98]. These fea- 

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The major areas of application of reflectance spectroscopy have been the elucidation of reaction mechanisms, double layer studies, investigations of underpotential deposition (UPD), and studies of the electroreflectance effect (ER). This range is too large for an in depth discussion to be given here. Instead, two examples of the type of information that can be obtained will be described (a third system, hydrogen adsorption on platinum, has been discussed in Chapter 7). Those readers interested in more details are referred to a recent review [1], and the literature cited therein. 

EQMB, EQCM Electrochemical quartz microbalance ERS Electroreflectance spectroscopy... 

Kolb and Franke have demonstrated how surface reconstruction phenomena can be studied in situ with the help of potential-induced surface states using electroreflectance (ER) spectroscopy.449,488,543,544 The optical properties of reconstructed and unreconstructed Au(100) have been found to be remarkably different. In recent model calculations it was shown that the accumulation of negative charges at a metal surface favors surface reconstruction because the increased sp-electron density at the surface gives rise to an increased compressive stress between surface atoms, forcing them into a densely packed structure.532... 

Potential-modulated UV-vis reflectance spectroscopy, often referred to as electroreflectance (ER), was originally developed in solid-state physics to characterize surfaces and was applied to studies of the electronic band structure of semiconductors. The ER technique has also been used to characterize metal electrode surfaces in the absence and presence of adsorbates. The reflectivity of metal electrodes is a function of the surface charge density of the electrodes. ER technique has also been used to investigate electrode reactions of organic species adsorbed on the electrode surfaces. Several review articles on ER are available [21-24]. 

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