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.

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.

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 3P139 Terahertz Attenuated Total Reflection Spectroscopy of liquid water and solutions

2005 ◽  
Vol 45 (supplement) ◽  
pp. S238
Author(s):  
A. Kenmochi ◽  
T. Tanabe ◽  
Y. Oyma ◽  
K. Suto ◽  
J. Nishizawa ◽  
...  
Keyword(s):  
Liquid Water ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Reflection Spectroscopy

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.

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