Measurement of the complex refractive index of liquids in the infrared using spectroscopic attenuated total reflection ellipsometry: correction for depolarization by scattering

1995 ◽  
Vol 34 (25) ◽  
pp. 5708 ◽  
Author(s):  
J. H. W. G. den Boer ◽  
G. M. W. Kroesen ◽  
F. J. de Hoog
Keyword(s):  
Refractive Index ◽  
Complex Refractive Index ◽  
Total Reflection ◽  
Attenuated Total Reflection

scholarly journals Using Attenuated Total Reflection (ATR) Apparatus to Investigate the Temperature Dependent Dielectric Properties of Water, Ice, and Tissue-Representative Fats

2021 ◽  
Author(s):  
Zoltan Vilagosh ◽  
Alireza Lajevardipour ◽  
Dominique Appadoo ◽  
Saulius Juodkazis ◽  
Andrew Wood
Keyword(s):  
Refractive Index ◽  
Dielectric Properties ◽  
Liquid Water ◽  
Complex Refractive Index ◽  
Rapid Change ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Temperature Dependent ◽  
Minimal Sample ◽  
Emulsified Water

A novel method of investigating the temperature dependent variation of aspects of the complex refractive index n* in samples in the THz range using continuous, non-polarised, synchrotron radiation is presented. The method relies on the use of ATR apparatus, and retains the advantage of minimal sample preparation, which is a feature of ATR techniques. The method demonstrates the viability of rapidly monitoring temperature reflectance whilst continuously heating or cooling samples by using a temperature variable Thermal Sample Stage. The method remains useful when the refractive index of the sample precludes attenuated total reflection study. This is demonstrated with the water reflectance experiments. The temperature dependent ATR reflectance of tissue-representative fats (lard and Lurpak® butter) was investigated with the novel approach. Both are within the ATR range of the diamond crystal in a “true” ATR mode. Lard showed no clear temperature variation between -15 0C and 24 0C at 0.7 to 1.15 THz or 1.70 to 2.25 THz. Lard can be regarded as having invariable, constant, dielectric properties within mixtures when biological substances are being assessed for temperature dependent dielectric variation within the stated THz ranges. Lurpak® butter (water content 14.7%) displayed temperature dependent reflectance features with a steady decline in reflectivity with increasing temperature. This is in line with the temperature-dependent behaviour of liquid water. There is no rapid change in reflectance, even at -20 0C, suggesting that emulsified water retains liquid-water-like THz properties at freezing temperatures.

Absolute Absorption Intensity and Dispersion Measurements on Some Organic Liquids in the Infrared

1980 ◽  
Vol 34 (6) ◽  
pp. 657-691 ◽  
Author(s):  
T. G. Goplen ◽  
D. G. Cameron ◽  
R. N. Jones
Keyword(s):  
Thin Films ◽  
Refractive Index ◽  
Complex Refractive Index ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Organic Liquids ◽  
Absorption Coefficients ◽  
Absorption Intensity ◽  
Transmission Measurements ◽  
Infrared Absorption Spectra

The infrared absorption spectra and corresponding dispersion spectra of the following liquids have been measured over the range 4200 to 250 cm−1: cyclo-C5H10, CH3·NO2, CH3·CN, CH2Br2, CH2Cl2, CBrCl3, CCl4, C6H6, C6H5·CH3, C6H5Cl, C6H5Br, C6H5I, and C6F6. The spectra were measured in the absence of solvent and the results are reported as the real and imaginary components of the complex refractive index ( n, k). The experimental technique combines transmission measurements through thin films and attenuated total reflection measurements by a method which has been described previously. The complete spectral and dispersion curves are displayed graphically; the absorption maxima are tabulated as absorption indices ( kmax) and as molar absorption coefficients (εmax). The dispersion extrema ( nmin, nmax) are also listed and the experimental uncertainties in these quantities are evaluated. Provision is made to supply the complete optical constant data on magnetic tape at encoded intervals of 0.5 cm−1.

Optical Depth Profiling by Attenuated Total Reflection Fourier Transform Infrared Spectroscopy: A New Approach

1996 ◽  
Vol 50 (9) ◽  
pp. 1187-1195 ◽  
Author(s):  
Sanong Ekgasit ◽  
Hatsuo Ishida
Keyword(s):  
Refractive Index ◽  
Fourier Transform ◽  
Infrared Spectroscopy ◽  
Fourier Transform Infrared Spectroscopy ◽  
Complex Refractive Index ◽  
Depth Profiling ◽  
Refractive Index Profile ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Index Profile

A new analytical technique for depth profiling using multiple-angle attenuated total reflection Fourier transform infrared spectroscopy has been developed. The analysis does not require prior knowledge of the profile of the complex refractive indices with respect to depth from the surface for the depth profiling calculation. This depth profiling analysis consists of two steps. First, the estimated complex refractive index profile is obtained by solving a set of linear equations of absorptance. Second, the reflectances from experiment are non-linearly fitted with those from exact optical theory. The estimated complex refractive index profile from the first step is used as a trial profile for the fitting. The converged complex refractive index profile from the fitting is then defined as the reconstructed complex refractive index profile of the film. The noise-added reflectances are used as experimental data to show the applicability of the new analytical approach.

Characteristic Properties Of Attenuated Total Reflection Spectroscopy In Terahertz Region

2008 ◽  
Vol 3 (4) ◽  
pp. 97-112
Author(s):  
Vasily V. Gerasimov ◽  
Boris A. Knyazev
Keyword(s):  
Refractive Index ◽  
Radiation Source ◽  
Complex Refractive Index ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Direct Solution ◽  
Reflection Spectroscopy ◽  
Optimal Method ◽  
Terahertz Region ◽  
Source Spectra

Experiments on the attenuated total reflection spectroscopy in the terahertz region were carried out using two homemade modules with silicon prisms developed for Fourier spectrometers and a free electron laser as radiation source. Spectra of water, water solutions, perfluorodecaline, paraffine oil, and amino acid powders were recorded. Real and imaging parts of the refractive index were retrieved using Kronig-Kramers transform or by direct solution of Fresnel equations. For a monochromatic radiation source two measurements at two different incident angles, rather than for two polarizations, were found to be an optimal method for the complex refractive index determination.

scholarly journals Using Attenuated Total Reflection (ATR) Apparatus to Investigate the Temperature Dependent Dielectric Properties of Water, Ice, and Tissue-Representative Fats

2021 ◽  
Vol 11 (6) ◽  
pp. 2544
Author(s):  
Zoltan Vilagosh ◽  
Alireza Lajevardipour ◽  
Dominique Appadoo ◽  
Saulius Juodkazis ◽  
Andrew W. Wood
Keyword(s):  
Refractive Index ◽  
Dielectric Properties ◽  
Liquid Water ◽  
Signal Intensity ◽  
Complex Refractive Index ◽  
Rapid Change ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Temperature Dependent ◽  
Reflected Signal

A novel method of investigating the temperature dependent variation of aspects of the complex refractive index n* in samples in the THz range using continuous, non-polarised, synchrotron radiation is presented. The method relies on the use of ATR apparatus, and retains the advantage of minimal sample preparation, which is a feature of ATR techniques. The method demonstrates a “proof of concept” of monitoring temperature reflectance whilst continuously heating or cooling samples by using a temperature variable Thermal Sample Stage. The method remains useful when the refractive index of the sample precludes attenuated total reflection study. This is demonstrated with the water reflectance experiments. The temperature dependent ATR reflectance of tissue-representative fats (lard and Lurpak® butter) was investigated with the novel approach. Both are within the ATR range of the diamond crystal in a “true” ATR mode. Lard showed no clear temperature variation between −15 °C and 24 °C at 0.7 to 1.15 THz or 1.70 to 2.25 THz. Lard can be regarded as having invariable, constant, dielectric properties within mixtures when biological substances are being assessed for temperature dependent dielectric variation within the stated THz ranges. Lurpak® butter (water content 14.7%) displayed temperature dependent reflected signal intensity features with a steady decline in reflectivity with increasing temperature. This is in line with the temperature-dependent behaviour of liquid water. There is no rapid change in reflected signal intensity even at −20 °C, suggesting that emulsified water retains liquid-water-like THz properties at freezing temperatures.

scholarly journals Characterisation of Biological Materials at THz Frequencies by Attenuated Total Reflection: Lard

2020 ◽  
Vol 10 (23) ◽  
pp. 8692
Author(s):  
Zoltan Vilagosh ◽  
Alireza Lajevardipour ◽  
Dominique Appadoo ◽  
Soon Hock Ng ◽  
Saulius Juodkazis ◽  
...  
Keyword(s):  
Penetration Depth ◽  
Evanescent Wave ◽  
Total Internal Reflection ◽  
Complex Refractive Index ◽  
Biological Tissues ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Frustrated Total Internal Reflection ◽  
Model Sample ◽  
Difference Time

The penetration depth of an evanescent wave in Attenuated Total Reflection (ATR) is dependent on the wavelength of the radiation utilised. At THz frequencies, the penetration depth into biological tissues is in the order of 0.1 to 0.5 mm; rendered pig lard was used as a model sample in this study. A method for the direct measurement of the evanescent wave penetration depth is presented which allows for the estimation of the dispersion of the complex refractive index by using the reflection of the evanescent wave from varying sample depths. The method employs frustrated total internal reflection, and has been demonstrated by using the THz/Far-IR beamline at the Australian synchrotron, and modelled using finite difference time domain (FDTD) simulations.

Determination and Use of Secondary Infrared Intensity Standards

1995 ◽  
Vol 49 (12) ◽  
pp. 1821-1825 ◽  
Author(s):  
John E. Bertie ◽  
Shuliang L. Zhang ◽  
R. Norman Jones ◽  
Yoram Apelblat ◽  
C. Dale Keefe
Keyword(s):  
Complex Refractive Index ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Infrared Analysis ◽  
Effective Number ◽  
Cell Constant ◽  
International Union ◽  
Absolute Intensities ◽  
Infrared Intensity ◽  
Chemistry Division

The presentation of absorption intensities in infrared spectra is usually limited to relative intensities instead of absolute intensities. The measurement of absolute intensities can be facilitated by the use of secondary intensity standards. Such standards have been accepted by the Commission on Molecular Structure and Spectroscopy and the Physical Chemistry Division of the International Union of Pure and Applied Chemistry and were published recently. The secondary standards are based on the complex refractive index and molar absorption coefficient spectra of benzene, chlorobenzene, toluene, and dichloromethane. They have been used in this laboratory to calibrate the effective pathlength of a transmission cell and the effective number of reflections in a Circle® multiple attenuated total reflection cell. A computer program, IRYTRUE, has been developed to standardize the routine use of these intensity standards to calibrate the effective pathlength of a transmission cell. The program has been used to calibrate three transmission cells. The agreement between the calibrated values of the effective pathlength obtained from the use of different standard band groups was determined. The calibrated cell pathlength agrees with that calculated from the interference fringe pattern of the empty cell within 3% for very thin cells and within 1% for cells thicker than 100 μm. We propose that the effective pathlength evaluated in this manner be called the cell constant, and that this cell constant be used in place of the pathlength in quantitative infrared analysis. The calibration of multiple attenuated total reflection measurements in the Circle cell has been achieved in two ways: by the use of peak heights and by the use of areas. Programs PCCALC and CIRCLCAL and its associated program RSCALC are described for this purpose. The intensity standards allow one to measure absolute infrared absorption intensities of liquids with confidence to an estimated accuracy of 2–3% by either transmission or calibrated ATR methods.

Improvements in the Use of Attenuated Total Reflection Fourier Transform Infrared Dichroism for Measuring Surface Orientation in Polymers

1997 ◽  
Vol 51 (8) ◽  
pp. 1083-1091 ◽  
Author(s):  
Neil J. Everall ◽  
Arran Bibby
Keyword(s):  
Refractive Index ◽  
Fourier Transform ◽  
Fourier Transform Infrared ◽  
Surface Orientation ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Specular Reflectance ◽  
Measuring Surface ◽  
Ft Ir ◽  
Orientation Parameters

Improvements in the use of attenuated total reflection (ATR) Fourier transform infrared (FT-IR) dichroism for measuring surface orientation in polymer films are described, with poly(ethylene terephthalate) (PET) as an example material. It is shown that normalizing band intensities relative to a nondichroic band, prior to calculating dichroic ratios, eliminates the need to maintain identical contact areas/pressures when removing, rotating, and reclamping samples to the ATR element, which has been a major historical drawback to this technique. The normalization is vital; it makes the calculated dichroic ratios largely insensitive to variations in sample/prism contact area, and less sensitive to uncertainties in the refractive indices and birefringence of the polymer. For PET, it is shown that the birefringence can be neglected in the analysis, and a single approximate refractive index used. This is a significant benefit since the birefringence will vary as a function of orientation and crystallinity. Polymers that are much more birefringent than PET can also be analyzed by using the formalism described in this paper, provided that the three independent indices are known. This paper is presented in two parts; first, equations are derived which allow the calculation of all second-order orientation parameters ( P200, P220, P202, and P222), and the averaged squared direction cosines, from the normalized ATR dichroic ratios. Second, we show how a single-reflection diamond ATR unit is an ideal tool for this work, since it allows small, hard, or irregularly shaped samples to be examined without fear of damaging the ATR element. We illustrate the technique using data obtained from a series of uniaxially drawn films, and one biaxially drawn film, using a commercially available accessory. From these data, orientation parameters were calculated as a function of draw ratio and compared with those obtained from specular-reflectance FT-IR and birefringence analysis of the same samples. The method should be applicable to any polymer provided that (1) a suitable nondichroic band is available for normalization and (2) the largest polymer refractive index lies well below that of the ATR element (2.4 in the case of diamond). It must be realized that condition 1 is not trivial; careful investigation is required to identify truly nondichroic bands (if any exist for the polymer of interest).

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