Abstract Attenuated Total Reflection Research Articles

Evidence of Light Depolarization in Grazing Incidence Germanium Attenuated Total Reflection Prisms

Attenuated total reflection (ATR) infrared absorption spectroscopy is a well-known vibrational spectroscopy technique for many different applications. In recent years this technique has been used to detect thin layer(s) lying on a solid substrate. Such a sample needs high pressure to ensure good optical contact between sample and prism and a p-polarization to enhance the signal to be detected. Such conditions have not been detailed in the literature regarding the effect of high pressure on the ATR measurement. This study shows the detrimental effect of high pressure on the ATR spectra. This effect is related to light depolarization induced by the germanium prism under high pressure. Moreover, the importance of polarizer position in the optical bench is highlighted. Indeed, due to the pressure-induced depolarization of the prism, the polarizer has to be placed before the prism to limit undesirable effects on the ATR spectrum baseline.

Attenuated Total Reflection Fourier Transform Infrared Spectroscopic Investigation of the Postmortem Metabolic Process in Rat and Human Kidney Cortex

Attenuated total reflection (ATR) Fourier transform infrared (FT-IR) spectroscopy has been applied to study the short and long term postmortem metabolic processes in rat and human kidney cortexes. The goals of this project were as follows: (1) to investigate the changes of ATR spectra in different rat and human tissues after death, (2) to explore the best mathematical model with different band absorption ratio changes to determine the postmortem interval (PMI), and (3) to establish a preliminary human postmortem ATR spectra database. There were three different types of metabolic changes after death based on the spectral results: (1) the intensities of some bands increased continuously (e.g., C-H stretching region), (2) the intensities of other bands decreased continuously (e.g., PO(2)(-) symmetric stretching), and (3) other bands remained relatively stable (e.g., C-OH bending, CO-O-C antisymmetric stretching). The band absorbance ratios for rats were found to display either a significant increase or decrease with increasing time after death. Of the absorbance ratios of the various bands investigated to find the best fit with the cubic model function in rats, the A(1652)/A(1396) ratio showed the strongest correlation (R(2) = 0.937). Comparison of the rat kidney cortex spectra with selected human postmortem cases showed similar postmortem metabolic changes. In conclusion, ATR FT-IR spectroscopy was shown to be a convenient and reliable method of determining short and long term postmortem intervals by simultaneously monitoring several specific parameters, although these observations have yet to be applied at forensic scenes by further field studies.

Effect of Molecular Weight on the Mutual Diffusion Process in Polystyrene/Poly(Vinyl Methyl Ether) System

Attenuated Total Reflection (ATR) spectroscopy was used to study the interdiffusion mechanism at the interface of Polystyrene (PS) and Poly(vinyl methyl ether) (PVME), at temperatures above and below the glass transition temperature (Tg) of PS, but in the miscible region. One molecular weight of PVME and 13 molecular weights of PS, both below and above the critical molecular weights of PS were used to investigate the effect of molecular weight on mutual diffusion process both below and above the critical molecular weight for entanglements of PS. To extract the diffusion coefficient from experimental data, we used the approach suggested by Jabbari and Pepas. Both Fickian and Case-II diffusion were necessary to fit the PVME concentration profile for the various molecular weights. The experimental results were also compared with the slow-mode and the fast mode theories2-3.

Single Fiber Analysis by Internal Reflection Infrared Microspectroscopy

Attenuated total reflection (ATR) is a convenient mode for single fiber analysis by infrared microspectroscopy, particularly when transmission spectra are difficult to obtain or when surface preferenced sampling is desirable. Textile finishes such as spin finishes, anti-static finishes, and permanent press finishes are revealed by ATR techniques. Bicomponent fibers may be analyzed by a combination of ATR techniques, transmission techniques, and spectral subtraction.

Attenuated Total Reflection Properties and Complex Dielectric Constants in Azobenzene LB Films Adsorbing Cyanine Dyes

Attenuated total reflection (ATR) properties have been investigated for azobenzene LB films adsorbing cyanine dyes on aluminum thin films. The ATR properties changed as the LB films were annealed. From the ATR properties, the complex dielectric constants were calculated as a uniaxial anisotropic dielectrics. It was thought that the ATR properties and the dielectric constants were caused by the dispersion properties due to the absorption bands.

Nonlinear optical properties due to the thermal effect in a prism-coupled ZnS thin film

Attenuated total reflection (ATR) and an optical nonlinear response were experimentally demonstrated in a prism-coupled ZnS thin film with a cw Ar+ laser. A high-index-glass-prism–Ag–ZnS–silica-glass configuration was fabricated by sequential deposition of ZnS and Ag thin films onto a silica glass substrate and with a high-index glass prism brought into contact with the films-coated substrate. Remarkable nonlinearity and hysteresis in relation to the incident power versus the reflected power were also realized because the reflectance near the ATR condition significantly depends on the refractive index of ZnS, which depends on the reflectance. By calculation of the optical and thermal properties of the configuration adopted in the experiment, the change in the refractive index of ZnS was confirmed to be due to the temperature rise resulting from the absorption of the incident light.

Infrared atr study on surface induced FLC alignment: Cell-gap dependence

Abstract Attenuated total reflection (ATR) infrared absorption spectroscopy has been used to study the effect of substrates on the alignment of MHOPOB ferroelectric liquid crystal molecules in the chiral smectic C phase as a function of the sample thickness. This method has enabled us to observe the influence of both the prism- and opposite-side substrates on the molecular alignment in the boundary layer about lμ thick at the prism-side substrate. In particular, the thickness dependence of a parallel alignment induced by the rubbing of polymer film substrates is discussed based on the polarization analysis of the ATR spectra and band assignments.