The Optical Constants of Coal, Char, and Limestone

1984 ◽  
Vol 106 (4) ◽  
pp. 678-683 ◽  
Author(s):  
M. Q. Brewster ◽  
T. Kunitomo
Keyword(s):  
Room Temperature ◽  
Optical Constants ◽  
Spherical Particles ◽  
Molecular Vibration ◽  
Molecular Absorption ◽  
Free Electrons ◽  
Absorption Bands ◽  
Specular Reflectance ◽  
Order Of Magnitude ◽  
Reflectance Measurements

The infrared optical constants, n and k, (n˜ = n − ik) of swelling and nonswelling coals, their respective char products, and limestone at room temperature have been obtained by a particle extinction technique using compressed KBr tablets. By assuming spherical particles and using Mie theory for the particle extinction measurements in conjunction with normal specular reflectance measurements from polished specimens, it is possible to obtain more accurate values for n and k than if the usual Fresnel reflectance technique is misapplied to samples that may appear specular but do not satisfy the stringent conditions necessary for invoking the Fresnel equations. Values of k for coal were found to be an order-of-magnitude smaller than previously reported values, with absorption due mainly to molecular vibration. The results for char evidenced that a significant increase in absorption by free electrons takes place upon devolatization and carbonization of coal. The limestone results demonstrated pronounced molecular absorption bands characteristic of CaCO3.

Calculation of Spectral Optical Constants Using Combined Ellipsometric and Reflectance Methods for Smooth and Rough Bulk Samples

2021 ◽  
pp. 000370282110478
Author(s):  
Gilles Fortin
Keyword(s):  
Rough Surface ◽  
Optical Constants ◽  
Sample Surface ◽  
Infrared Region ◽  
Homogeneous Sample ◽  
Specular Reflectance ◽  
Scattering Effects ◽  
Spectral Ranges ◽  
Reflectance Measurements ◽  
Polarized Reflectance

Spectra of the optical constants n and k of a substance are often deduced from spectroscopic measurements, performed on a thick and homogeneous sample, and from a model used to simulate these measurements. Spectra obtained for n and k using the ellipsometric method generally produce polarized reflectance simulations in strong agreement with the experimental measurements, but they sometimes introduce significant discrepancies over limited spectral ranges, whereas spectra of n and k obtained with the single-angle reflectance method require a perfectly smooth sample surface to be viable. This paper presents an alternative method to calculate n and k. The method exploits both ellipsometric measurements and s-polarized specular reflectance measurements, and compensates for potential surface scattering effects with the introduction of a specularity factor. It is applicable to bulk samples having either a smooth or a rough surface. It provides spectral optical constants that are consistent with s-polarized reflectance measurements. Demonstrations are performed in the infrared region using a glass slide (smooth surface) and a pellet of compressed ammonium sulfate powder (rough surface).

Optische Eigenschaften von natürlichen und künstlichen Bleichromateinkristallen

1968 ◽  
Vol 23 (12) ◽  
pp. 2014-2018 ◽  
Author(s):  
Franz Rudolf Kessler ◽  
Parvin Daneschfar
Keyword(s):  
Activation Energy ◽  
Refractive Index ◽  
Absorption Band ◽  
Optical Constants ◽  
Charge Carriers ◽  
Free Charge ◽  
Free Electrons ◽  
Absorption Bands ◽  
Unpolarised Light ◽  
No Absorption

Out of solution artificial PbCrO4-single-crystals, monoclin modification, equal to natural Crocoit have been produced. The optical constants for natural and these artificial crystals have been found to be equal by measurements of reflectivity and transmission with unpolarised light in the range 0.3 — 15 µm perpendicular to the (110) -plain. Between 1 and 8 µm the refractive index is constant (n = 2,1). In this region some absorption bands occur (2.8 µm corresponding to the donator activation energy of 0.44 eV and 6 μm). At 0.45 µm there is another absorption band but no absorption edge, which was expected with respect to the photoconductivity. Above 8 µm the optical constants are determined by the reststrahlen band at 11.3 μm. The absorption of free charge carriers is discussed because leadchromate in the literature is known to be a purely electronical conductor. An influence of the free charge carriers in the tested spectral range could not be recognized. From this fact it is possible to give some estimations about the conductivity mechanism respectively the mobility of the free electrons.

New Technique for Determining the Optical Constants of Liquids

2002 ◽  
Vol 56 (7) ◽  
pp. 928-934 ◽  
Author(s):  
C. Dale Keefe ◽  
Jason K. Pearson
Keyword(s):  
Optical Constants ◽  
Reflectance Spectrum ◽  
Strong Absorption ◽  
New Technique ◽  
Attenuated Total Reflectance ◽  
Absorption Bands ◽  
Total Reflectance ◽  
Specular Reflectance ◽  
Volatile Liquids ◽  
Atr Spectroscopy

The traditional techniques of transmission and attenuated total reflectance (ATR) spectroscopy for determining the optical constants of liquids are not practical or reliable for very strong absorption bands. Specular reflectance can be used in these cases, but for volatile liquids it is impossible to separate the reflectance spectrum of the liquid from the absorption spectrum of the vapor above the liquid. Methods using special cells have been described in the literature to prevent the liquid from evaporating. In this paper, a similar technique that makes use of traditional transmission cells is presented. It is shown that this new technique generates k(ν˜) spectra for strong absorption bands that are accurate to approximately 2%.

Polarimetric Observations of Red Variables: A Study of Gas and Particle Interactions

1979 ◽  
Vol 46 ◽  
pp. 386-408 ◽  
Author(s):  
G. V. Coyne ◽  
I. S. McLean
Keyword(s):  
Wavelength Dependence ◽  
Stellar Atmosphere ◽  
Molecular Absorption ◽  
Absorption Bands ◽  
Absorption And Emission ◽  
Mira Variables ◽  
Stellar Photosphere ◽  
Regular Variable ◽  
Red Supergiants ◽  
Balmer Lines

AbstractIn recent years the wavelength, dependence of the polarization in a number of Mira variables, semi-regular variables and red supergiants has been measured with resolutions between 0.3 and 300 A over the range 3300 to 11000 A. Variations are seen across molecular absorption bands, especially TiO bands, and across atomic absorption and emission lines, especially the Balmer lines. In most cases one can ignore or it is possible to eliminate the effects due to interstellar polarization, so that one can study the polarization mechanisms operating in the stellar atmosphere and environment. The stars Omicron Ceti. (Mira), V CVn (semi-regular variable) and Mu Cephei (M2 la), in addition to other stars similar to them, will be discussed in some detail.Models to explain the observed polarization consider that the continuum flux is polarized either by electron, molecular and/or grain scattering or by temperature variations and/or geometrical asymmetries over the stellar photosphere. This polarized radiation is affected by atomic and molecular absorption and emission processes at various geometric depths in the stellar atmosphere and envelope. High resolution spectropolarimetry promises, therefore, to be a power-rul tool for studying stratification effects in these stars.

Luminescence Properties of Europium-Doped Yttrium Oxides Derived from Their Dodecylsulfate-Templated Mesostructure and Nanotube Forms

2003 ◽  
Vol 775 ◽  
Author(s):  
Tsuyoshi Kijima ◽  
Kenichi Iwanaga ◽  
Tomomi Hamasuna ◽  
Shinji Mohri ◽  
Mitsunori Yada ◽  
...  
Keyword(s):  
Room Temperature ◽  
Broad Band ◽  
Concentration Quenching ◽  
Precipitation Method ◽  
Homogeneous Precipitation ◽  
Bulk Materials ◽  
Main Band ◽  
Homogeneous Precipitation Method ◽  
Order Of Magnitude ◽  
Weak Luminescence

AbstractEuropium-doped hexagonal-mesostructured and nanotubular yttrium oxides templated by dodecylsulfate species as well as surfactant free bulk oxides were synthesized by the homogeneous precipitation method. All the as grown nanostructured or bulk materials with amorphous or poorly crystalline frameworks showed weak luminescence bands at room temperature. On calcination at 1000°C these materials were converted into highly crystalline yttrium oxides, resulting in a total increase in intensity of all the bands by one order of magnitude. In the hexagonal-mesostructured system, the main band due to the 5D0-7F2 transition for the calcined phases showed a sharp but asymmetrical multiplet splitting indicating multiple Eu sites. Concentration quenching was found at a Eu content of 3 mol% or above for these phases. In contrast, the main emission for the calcined solids in the nanotubular system occurred as poorly resolved broad band and the intensity of the main band at higher Eu content was significantly enhanced compared with those for the other two systems.

Temperature Dependence of the Self-Assembled Styrene Based Random Ionomers in Aqueous Solution

2003 ◽  
Vol 775 ◽  
Author(s):  
Sung-Hwa Oh ◽  
Ju-Myung Song ◽  
Joon-Seop Kim ◽  
Hyang-Rim Oh ◽  
Jeong-A Yu
Keyword(s):  
Partition Coefficients ◽  
Room Temperature ◽  
Aqueous Media ◽  
The Self ◽  
Spectroscopic Methods ◽  
Ion Content ◽  
Repeat Units ◽  
Notable Effect ◽  
Order Of Magnitude ◽  
Experimental Errors

AbstractSolution behaviors of poly(styrene-co-sodium methacrylate) were studied by fluorescence spectroscopic methods using pyrene as a probe. The mol% of methacrylate was in the range 3.6–9.4. Water and N,N-dimethylforamide(DMF) mixture was used as a solvent (DMF/water = 0.2 mol %). The critical micelle (or aggregation) concentrations of ionomers and the partition coefficients of pyrene were obtained the temperature range 10–80°C. At room temperature, the values of CMCs (or CACs) were in the range 4.7 ×10-6 5.3 ×10-6 g/mL and we could not find any notable effect of the content of ionic repeat units within the experimental errors. Unlike CMCs, as the ion content increased, partitioning of pyrene between the hydrophobic aggregates and an aqueous media decreased from 1.5 ×105 to 9.4 ×104. As the temperature increased from 10 to 80 °C, the values of CMCs increased less than one order of magnitude. While, the partition coefficients of pyrene decreased one order of magnitude and the effect of the ion content became negligible.

scholarly journals Mechanistic Study on Gold-Like Luster Development of Solution-Cast Oligo(3-methoxythiophene) Film

Coatings ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 861
Author(s):  
Minako Kubo ◽  
Minako Tachiki ◽  
Terumasa Mitogawa ◽  
Kota Saito ◽  
Ryota Saito ◽  
...  
Keyword(s):  
Microscopic Analysis ◽  
Mechanistic Study ◽  
Free Electrons ◽  
Coating Films ◽  
Electron Microscopic ◽  
Regular Structures ◽  
Scanning Electron Microscopic ◽  
Solution Cast ◽  
Scanning Electron Microscopic Analysis ◽  
Reflectance Measurements

Solution-cast coating films of perchlorate-doped oligo(3-methoxythiophene) exhibited a gold-like luster similar to that of metallic gold despite the involvement of no metals. However, the development mechanism of the luster remains ambiguous. To understand the mechanism, we performed scanning electron microscopic analysis, variable-angle spectral reflectance measurements, and ellipsometry measurements on ClO4−-doped oligo(3-methoxythiophene) cast film with a gold-like luster. The results revealed that the lustrous color of the film was not induced by the submicron-sized regular structures (structural color), nor by the high-density free electrons (reflective response based on Drude model), but by the large optical constants (refractive index and extinction coefficient) of the film, as speculated previously.

Structure and Conductivity of Iodine-Doped C60 Thin Films

1994 ◽  
Vol 359 ◽  
Author(s):  
Jun Chen ◽  
Haiyan Zhang ◽  
Baoqiong Chen ◽  
Shaoqi Peng ◽  
Ning Ke ◽  
...  
Keyword(s):  
Thin Films ◽  
Electrical Conductivity ◽  
Room Temperature ◽  
Conductivity Measurements ◽  
X Ray Diffraction ◽  
Temperature Conductivity ◽  
Room Temperature Conductivity ◽  
X Ray ◽  
Thermally Activated ◽  
Order Of Magnitude

ABSTRACTWe report here the results of our study on the properties of iodine-doped C60 thin films by IR and optical absorption, X-ray diffraction, and electrical conductivity measurements. The results show that there is no apparent structural change in the iodine-doped samples at room temperature in comparison with that of the undoped films. However, in the electrical conductivity measurements, an increase of more that one order of magnitude in the room temperature conductivity has been observed in the iodine-doped samples. In addition, while the conductivity of the undoped films shows thermally activated temperature dependence, the conductivity of the iodine-doped films was found to be constant over a fairly wide temperature range (from 20°C to 70°C) exhibiting a metallic feature.

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