Variable-Angle Reflectance Measurements in the Infrared

1968 ◽  
Vol 22 (5) ◽  
pp. 460-463
Author(s):  
Donald E. McCarthy
Keyword(s):  
Optical Constants ◽  
Incident Angle ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Angle Of Incidence ◽  
Reflection Spectra ◽  
The Relationship ◽  
Collimated Beam ◽  
Reflectance Measurements

Reflection measurements in the infrared are useful in the determination of optical constants of materials, reststrahlen peaks, efficiency of black paints, and attenuated total reflection studies. While many papers have dealt with reflection, few have investigated the effect of the angle of incidence upon the reflection spectra. Besides angle of incidence, another important factor is the use of a collimated beam. Both of these parameters must be known and controlled for best results. Some results illustrating the effect of varying the incident angle on samples are discussed, as well as the relationship between angle of incidence and polarization.

Subsurface Layer Studies by Attenuated Total Reflection Fourier Transform Spectroscopy

1977 ◽  
Vol 31 (4) ◽  
pp. 289-292 ◽  
Author(s):  
Tomas Hirschfeld
Keyword(s):  
Fourier Transform ◽  
Critical Angle ◽  
Subsurface Layer ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Data Sets ◽  
Angle Of Incidence ◽  
Reflection Spectra ◽  
Reflection Spectroscopy ◽  
A New Technique

In total reflection spectroscopy the effective sampled depth increases as the angle of incidence approaches the critical one. At each angle of incidence, successive layers within the sample are weighed differently in the overall spectrum, and the manner of this weighing changes with angle. It is thus possible in principle to deconvolute a set of spectra taken at different angles into spectra corresponding to successive depth invervals. As this angular effect is particularly marked near the critical angle, where attenuated total reflection spectra are severely distorted, the spectra usually require inversion into optical constant spectra. This has been done by a new technique that measures spectra twice at each angle with different prism materials to give the necessary data sets. Examples of such subsurface spectra are shown.

A Reflection Spectrophotometer for the Measurement of the Optical Constants of Liquids in the Infrared

1980 ◽  
Vol 34 (6) ◽  
pp. 646-651 ◽  
Author(s):  
D. G. Cameron ◽  
D. Escolar ◽  
T. G. Goplen ◽  
A. Nadeau ◽  
R. P. Young ◽  
...  
Keyword(s):  
Optical Constants ◽  
Quantitative Measurement ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Reflection Spectra ◽  
Infrared Band ◽  
Infrared Spectrophotometer ◽  
Design And Construction

The design and construction of an infrared spectrophotometer for the quantitative measurement of attenuated total reflection spectra are described. The instrument is used to determine the optical constants of liquids as part of a study of infrared band shapes and intensities.

Attenuated-total-reflection technique for the determination of optical constants

1991 ◽  
Vol 30 (22) ◽  
pp. 3176 ◽  
Author(s):  
L. E. Regalado ◽  
R. Machorro ◽  
J. M. Siqueiros
Keyword(s):  
Optical Constants ◽  
Total Reflection ◽  
Attenuated Total Reflection

The Control of Errors in Infrared Spectrophotometry. VI. The Evaluation of Optical Constants by Combined Transmission and Attenuated Total Reflection Measurements

1980 ◽  
Vol 34 (6) ◽  
pp. 652-656 ◽  
Author(s):  
T. G. Goplen ◽  
D. G. Cameron ◽  
R. N. Jones
Keyword(s):  
Refractive Index ◽  
Optical Constants ◽  
Statistical Treatment ◽  
Statistical Error ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Integration Constant ◽  
The One ◽  
Improved Technique

An improved technique is described for the determination of the optical constants of liquids in the infrared. It is based on a combination of transmission and attenuated total reflection (ATR) measurements. A novel application of the Kramers-Kronig transform function is involved whereby a single-valued integration constant is derived from a vector of refractive index measurements obtained by ATR. These are measured over a wavenumber range where the absorbance is low. It has been shown in earlier work that by an appropriate choice of a low refractive index contact material (in our case sodium chloride) the ATR method has high precision and accuracy under these conditions. The accuracy of the method is evaluated on the basis of a statistical treatment of the propagation of the estimated errors in the experimentally measured quantities, viz., the transmittance, the cell thickness, and the ATR measurements which establish the integration constant (anchor point) of the Kramers-Kronig transform function. The transmittance measurements are made at several cell thicknesses. The data reduction computer program, by which the optical constants are evaluated from the transmission measurements, monitors these sets of data and selects at each wavenumber the one having the minimal statistical error.

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