Spectroscopy , internal reflection

N. J. Harrick, Internal Reflection Spectroscopy, ]olm. Wiley Sons, Inc., New York, 1967. 

Harrick, N.J., Internal Reflection Spectroscopy. Interscience Publishers, New York, NY, 1967, p. 30. 

IRS Internal reflectance spectroscopy LEI Laser-enhanced ionisation... 

Figure 3.1. Showing geometries for (a) RAIRS (IRAS), where 80° < 0 < 89° and (b) Multiple Internal Reflection spectroscopy (MIR), where 0 > 0criticai-...

Multiple Internal Reflection Spectroscopy (MIR) is an alternative approach in which the IR beam is passed through a thin, IR transmitting sample such that it undergoes total internal reflection alternately from the front and rear faces of the sample (Figure 3.1(b)). At each reflection, some of the IT radiation may be absorbed by species adsorbed on the solid surface. 

In materials investigations surface-sensitive techniques are of special interest. The major contribution of infrared spectroscopy to this field is internal reflection spectroscopy (IRS), often called the "attenuated total reflection" (ATR) technique. To describe theory and principle, electromagnetic wave theory must be apphed [33]. 

IR internal reflection spectroscopy can be used to distinguish the relative differences in the concentration of the slip additive at film surfaces. 

Harrick N. Internal Reflection Spectroscopy, 3rd Ed., Harrick Scientific Corp., 1987. 

Many compounds exhibit near-IR and mid-IR absorption. By using IR transparent optical fibers, detection of an absorption band in the IR region is possible for optical sensing. Both direct sensing using the absorption property of the analyte or indicator sensing are widely exploited. Most mid-IR sensing schemes are based on the principles of internal reflection spectroscopy, or the attenuated total reflection (ATR) [3,14-21],... 

Harrick, N.J. "Internal Reflection Spectroscopy" Harrick Scientific Corp. Ossining, NY, 1979. 

M. N. Kronick and W. A. Little, A new immunoassay based on fluorescence excitation by internal reflection spectroscopy, J. Immtmol. Methods 8, 235-240 (1975). 

F.M. Mirabella, Jr (ed.). Internal Reflection Spectroscopy Theory and Applications, Marcel Dekker, New York, Vol. 15, 1993. 

A good review article on optical constants and their measurement is that by Bell (1967). Determination of optical constants from reflectance measurements is treated by Wendlandt and Hecht (1966) and from internal reflection spectroscopy by Harrick (1967). Ellipsometric techniques are discussed at length by Azzam and Bashara (1977). 

Internal-reflection spectroscopy is used to obtain IR spectra of hard-to-handle or hard-to-prepare samples such as solids with limited solubility, films, pastes, adhesives, and powders. Reflection occurs when a beam of radiation passes from a denser to a less dense medium. The fraction of incident beam which is reflected increases as the angle of incidence becomes larger. Beyond a certain critical angle, reflection is complete. During the reflection process the beam penetrates a small distance into... 

The thicknesses of free soap films and liquid films adsorbed on surfaces (Figs. 1.26d and 1.26e), which can be measured using optical techniques such as reflected intensity, total internal reflection spectroscopy, or ellipsometry as functions of salt concentration or vapor pressure, can provide information on the long-range repulsive forces stabilizing thick wetting films. We see an example of this in Chapter 11. 

Internal reflection spectroscopy is widely applied for on-line process control. In this type of application, the chemical reactor is equipped with an internal reflection probe or an IRE. The goal of this type of application is the quantification of reactant and/or product concentrations to provide real-time information about the conversion within the reactor. In comparison with other analytical methods such as gas chromatography, high-pressure liquid chromatography, mass spectrometry, and NMR spectroscopy, ATR spectroscopy is considerably faster and does not require withdrawal of sample, which can be detrimental for monitoring of labile compounds and for some other applications. 

In internal reflection spectroscopy (IRS), the spectrum is obtained with the sample in optical contact with another material (e.g. a prism) and the beam is passed through the prism onto the sample. The prism is optically denser than the sample, the incoming light forms a standing wave pattern at the interface within the dense prism medium whereas in the sample (with the lower refractive index), the amplitude of the electric field falls off exponentially with the distance from the phase boundary. When the sample exhibits absorbance, the reflectance measured is given by ... 

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