Total internal reflection, description

Numerous books cover the topic of sampling methods in infrared spectroscopy (see, e.g., references [10-12]), and a detailed description of all the various alternatives is beyond the scope of this chapter. Instead, we will focus on the two sampling methods that are most commonly employed in food analysis applications, namely, the use of transmission cells for recording the spectra of solutions and the total internal reflection technique, also known as attenuated total reflectance (ATR). Readers who wish to learn about the techniques not covered here may consult the references cited above. 

On the other hand, optical microscopy, confocal microscopy, ellipsometry, scanning electron microscopy (SEM), scanning tunneling microscopy (STM), atomic force microscopy (AFM) and total internal reflection fluorescence (TIRF) are the main microscopic methods for imaging the surface structure. There are many good books and reviews on spectroscopic and chemical surface analysis methods and microscopy of surfaces description of the principles and application details of these advanced instrumental methods is beyond the scope of this book. 

Conversely, in the above example, the variation of the phase change with polarization of the plane wave electric field is small when the difference between and ng is small, although the incident wave is still totally reflected. Thus, if the refractive indices are nearly equal, the slight nonuniformity maintains total internal reflection, but the medium is virtually homogeneous as far as polarization effects are concerned. Further, the fields associated with plane-wave reflection satisfy the scalar wave equation, as discussed in Section 35-6. With this perspective, we anticipate that waveguides of arbitrary refractive-index profile have some analogous simplification in the description of their modal fields, provided only that the profile height parameter is small, i.e. A < 1, or n,. ... 

Electromoduiated Infrared Spectroscopy. The form most widely in use is the electromoduiated attenuated-total-reflection-spectroscopy. This is the electromoduiated form of the multiple internal reflection spectroscopy that was previously discussed. The practice here is to modulate, by switching the potential between two values, and monitor the absorption changes by lock-in techniques. Description of this technique with an emphasis on metal-electrolyte interfaces can be found in (70). The modulation here is different from all the other techniques that were mentioned in the sense that the modulation is not a small perturbation of an equilibrium state but a shift between two equilibrium states. Whether... 

---