Precise thickness and refractive index determination of polyimide films using attenuated total reflection

1994 ◽  
Vol 33 (34) ◽  
pp. 8036 ◽  
Author(s):  
L. Lévesque ◽  
B. E. Paton ◽  
S. H. Payne
Keyword(s):  
Refractive Index ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Polyimide Films

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.

Chemometric Approach to a Rapid Attenuated Total Reflection Fourier Transform Infrared Analysis of Complex Heroin-Based Mixtures

2020 ◽  
pp. 000370282096971
Author(s):  
Nataša Radosavljević Stevanović ◽  
Milena Jovanović ◽  
Federico Marini ◽  
Slavica Ražić
Keyword(s):  
Principal Component Analysis ◽  
Fourier Transform ◽  
Principal Component ◽  
Fourier Transform Infrared ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Illegal Market ◽  
Ft Ir

Heroin is one of the most frequently seized drugs in Southeastern Europe. Due to the position in the Balkan route, the Republic of Serbia keeps important role in suppression of the trafficking of heroin for domestic and foreign illegal market. This research is aimed to provide a good scientific approach in the field of seized heroin analysis. Two different forms of heroin are present in the illegal market, mostly in mixtures with typical “cutting” agents: caffeine, paracetamol, and sugars. It was observed that the quantity of pure heroin in seized samples slightly increases from year to year. The aim of this study was to produce a reliable and fast procedure for classification of illicit heroin samples and determination of the concentration range of heroin in the samples. For that purpose, the attenuated total reflection Fourier transform infrared spectroscopy (ATR FT-IR) technique was used and combined with such chemometric methods as principal component analysis, cluster analysis, and partial least squares. Principal component analysis (PCA) as an unsupervised model was used for exploratory purposes to identify trends, similarities, and differences between samples by reducing the dimensionality of the data. The cluster classification of examined samples turned out to be extremely useful to evaluate the possibilities of the ATR FT-IR technique to classify the samples appropriately into the patterns, the constituted clusters. Additionally, partial least square was the suitable method for the purpose of determination of the heroin hydrochloride concentration range in examined samples. It is proved that the joined application of spectroscopy and chemometrics can be extremely convenient and useful for forensic and drugs control laboratories.

The use of a slit in determining refractive indices with the microscope

1917 ◽  
Vol 18 (84) ◽  
pp. 130-132
Author(s):  
John William Evans
Keyword(s):  
Crystal Structure ◽  
Refractive Index ◽  
Optical Properties ◽  
Critical Angle ◽  
Total Reflection ◽  
Index Of Refraction ◽  
Refractive Indices ◽  
Object Image ◽  
Ordinary Object

Certain optical properties of crystals, and more particularly the refractive index, may be determined either in the directions-image, often referred to as the 'image in convergent light', or in the ordinary object-image in which the object itself is seen. In the former case, in which the index of refraction is 'usually determined by means of the critical angle of total-reflection, every point in the image corresponds to a single direction of propagation of the wave-front through the crystal-structure and to the two corresponding directions of vibration. One of these can, however, be eliminated by the insertion of a nicol in an approximate position, and thus all ambiguity in the determination of the refractive index is removed.

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