Determination of the spectra of the optical constants of bulk phases via Fourier transform ATR

Dignam, M. J.; Mamiche‐Afara, Suzanne

doi:10.1016/0584-8539(88)80195-8

Cited by 35 publications

(20 citation statements)

References 11 publications

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“…Thus, optical constants can be determined from only one experimental spectrum such as external reflection at near-normal incidence for bulk materials, 38,39 transmission at normal incidence for liquids and thin films deposited on solid substrates, [40][41][42][43][44][45][46][47][48][49] or ATR. [50][51][52][53][54][55][56][57][58][59] The transmission method is particularly valuable for weak and moderately strong bands, whereas the ATR method can be applied to strong bands using the correction algorithm developed by Dignam et al 54 In the present work, the possible distortions of the IR spectra of ILs are first described. Then a method using polarized ATR spectra is proposed to determine the optical constants in the mid-infrared (MIR).…”

Section: Introductionmentioning

confidence: 98%

Infrared Spectroscopy of Ionic Liquids: Quantitative Aspects and Determination of Optical Constants

2010

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The infrared (IR) spectra of ionic liquids involving 1-butyl-3-methylimidazolium (BMI) and the (CF(3)SO(2))(2)N(-), BF(4)(-), or PF(6)(-) anions, recorded in the transmission and attenuated total reflection (ATR) modes, exhibit strong differences in the most intense anion absorption profiles. These distortions come from optical effects and make difficult any quantitative analysis of, for example, the antisymmetric stretching vibrations of the BF(4)(-) and PF(6)(-) anions. A method is proposed to determine the optical constants, from which any type of experimental spectrum can be simulated. It is then possible to use the anion vibrational bands as spectroscopic probes of the local interactions occurring in the neat ionic liquids and in solutions. This is illustrated by a direct identification of ion pairs and separated ions in the IR spectra of BMI-PF(6) solutions.

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Section: Introductionmentioning

confidence: 98%

Infrared Spectroscopy of Ionic Liquids: Quantitative Aspects and Determination of Optical Constants

2010

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“…Iterative methods have been proposed to extract the complex refractive index from an ATR spectrum. 17,19,20 The imaginary part of the refractive index ( , the absorption coefficient) is estimated from the experimental spectrum; the real part of the refractive index, , is calculated through the Kramers-Kronig transform of ; and are used in the Fresnel equations to reproduce a predicted spectrum, which is compared to the measured spectrum and then used to generate a better estimate for . The accuracy of algorithm depends on the quality of the method used to guess , the accuracy of the numerical Kramers-Kronig transform, and the accuracy of the Fresnel calculation (for example, does it describe a system with the correct number of layers?…”

Section: Effect Of Atr On Band Shape and Positionmentioning

confidence: 99%

Total internal reflection spectroscopy for studying soft matter

Woods

Bain

2014

Soft Matter

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Total internal reflection (TIR) spectroscopy is a widely used technique to study soft matter at interfaces. This tutorial review aims to provide researchers with an overview of the principles, experimental design and applications of TIR spectroscopy to enable them to understand how this class of techniques might be used in their research. It also highlights limitations and pitfalls of TIR techniques, which will assist readers in critically analysing the literature. Techniques covered include attenuated total reflection infrared spectroscopy (ATR-IR), TIR fluorescence, TIR Raman scattering and cavity-enhanced techniques. Other related techniques are briefly described.

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“…This method was successfully applied by Karakassides et al for recovering the optical constants from the external reflectance spectra obtained at quasi-normal incidence (Karakassides et al 1997). Unlike normal reflectance experiments, in the case of ATR and because of the phase shift induced by reflections under total reflection conditions, the δi determined from ln(Ri 1/2 ) has to be corrected (Plaskett and Schatz 1963;Bardwell and Dignam 1985;Dignam 1988;Dignam and Mamiche-Afara 1988;Ohta and Ishida 1988;Buffeteau et al 1999; Boulet-Audet et al 2010). Dignam et al showed that this correction factor, Is,p, takes a particularly simple form that can be readily estimated.…”

Section: Spectral Simulationmentioning

confidence: 99%

“…Motivated by this statement, this work aims at providing ATR users with the necessary equations for computing the optical constants from polarized ATR measurement that can be further used for the quantitative interpretation of infrared spectra. The determination of the anisotropic optical constants is based on a Kramers-Kronig transform analysis applied to polarized ATR spectra of thick Na -SWy-3 montmorillonite film (Bardwell and Dignam 1985;Dignam and Mamiche-Afara 1988;Bertie and Lan 1996). These optical constants are then used to simulate spectra under a variety of conditions.…”

Section: Introductionmentioning

confidence: 99%

Optical Theory-Based Simulation of Attenuated Total Reflection Infrared Spectra of Montmorillonite Films

Grégoire

Dazas

Leloup

et al. 2020

Clays and clay miner.

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Infrared analyses of clay minerals samples are usually performed by transmission techniques. While transmission measurements are easy and inexpensive, the sample preparation plays a primordial role in the quality of the data. Alternatively, attenuated total reflection (ATR) provides a powerful and often simpler analysis method. However, the ATR spectra reveal strong differences when compared to transmission spectra leading sometimes to confusion in the interpretations. Indeed, optical effects play a prominent role in the ATR spectral profile and their identification is mandatory for obtaining quantitative information regarding molecular/particle orientation or film thickness. Here, exact spectral simulations of montmorillonite films are performed by making use of the optical theory, following the determination of the anisotropic optical constants from the experimental reflectance spectra by Kramers-Kronig transformation. This methodology can advantageously be used (i) to choose the appropriate optical conditions for advanced and reliable characterization of clay minerals, (ii) to extract quantitative information such as the estimation of the film thickness, and (iii) to discriminate optical phenomena (optical interferences) from chemical/structural features of the sample.

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Determination of the spectra of the optical constants of bulk phases via Fourier transform ATR

Cited by 35 publications

References 11 publications

Infrared Spectroscopy of Ionic Liquids: Quantitative Aspects and Determination of Optical Constants

Infrared Spectroscopy of Ionic Liquids: Quantitative Aspects and Determination of Optical Constants

Total internal reflection spectroscopy for studying soft matter

Optical Theory-Based Simulation of Attenuated Total Reflection Infrared Spectra of Montmorillonite Films

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