Determining the absolute concentration of a compound requires knowledge of the compound's absorption coefficient. The absorption coefficient for some compounds is available from reference sources, and it can also be determined by measuring the spectrum of a calibration standard with a known concentration of the target.
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Schwarzschild's equation has been expressed in different forms and symbols by different authors. The quantity nσλ is known as the absorption coefficient (βa), a measure of attenuation with units of cm−1. The absorption coefficient is fundamentally the product of a quantity of absorbers per unit volume (formally cm−3) times an efficiency of absorption (area/absorber, formally cm2). Several sources replace nσλ with kλr, where kλ is the absorption coefficient per unit density and r is the density of the gas.
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Acoustic waves can be absorbed. The amount of absorption is given by the absorption coefficient which is given by :\alpha = 1 - R^2 where :\alpha is the absorption coefficient without a unit :R is the reflection coefficient without a unit Often acoustic absorption of materials is given in decibels instead.
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Recent studies have demonstrated that CsPbBr3 nanocrystals have an absorption coefficient of 2x105 cm−1 at 335 nm and 8x104 cm−1 at 400 nm.
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This sort of modulation is called direct modulation, as opposed to the external modulation performed by a light modulator. For this reason, light modulators are called external light modulators. According to manipulation of the properties of material modulators are divided into two groups, absorptive modulators (absorption coefficient) and refractive modulators (refractive index of the material). Absorption coefficient can be manipulated by Franz- Keldysh effect, Quantum-Confined Stark Effect, excitonic absorption, or changes of free carrier concentration.
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However, in the latter case, the applied electric field changes the molar absorption coefficient of the sample, which can be measured using traditional absorption or emission spectroscopic methods. This effect is known as electrochromism.
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Absorptance of the surface of a material is its effectiveness in absorbing radiant energy. It is the ratio of the absorbed to the incident radiant power. This should not be confused with absorbance and absorption coefficient.
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For this reason, the PML absorption coefficient σ is typically turned on gradually from zero (e.g. quadratically) over a short distance on the scale of the wavelength of the wave. In general, any absorber, whether PML or not, is reflectionless in the limit where it turns on sufficiently gradually (and the absorbing layer becomes thicker), but in a discretized system the benefit of PML is to reduce the finite-thickness "transition" reflection by many orders of magnitude compared to a simple isotropic absorption coefficient. In certain materials, there are "backward- wave" solutions in which group and phase velocity are opposite to one another.
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According to the properties of the material that are used to modulate the light beam, modulators are divided into two groups: absorptive modulators and refractive modulators. In absorptive modulators the absorption coefficient of the material is changed, in refractive modulators the refractive index of the material is changed. The absorption coefficient of the material in the modulator can be manipulated by the Franz-Keldysh effect, the Quantum-confined Stark effect, excitonic absorption, changes of Fermi level, or changes of free carrier concentration. Usually, if several such effects appear together, the modulator is called an electro-absorptive modulator.
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SiCloud includes the common dielectrics and semiconductors for waveguide core, cladding, and photodetection, as well as metals for electrical contacts. In the Main Graph, one may examine several physical parameters of interest for each material, in different wavelength ranges, and choose between frequency and free-space wavelength for convenience. SiCloud also includes citations for the original data so that users may gather the raw data and be self-assured of its accuracy and conditions. For silicon in particular, SiCloud includes a large number of parameters beyond refractive index and absorption coefficient, including the thermo-optic coefficient, Raman gain coefficient, Kerr coefficient, and two-photon absorption coefficient.
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EXAFS spectra are displayed as plots of the absorption coefficient of a given material versus energy, typically in a 500 – 1000 eV range beginning before an absorption edge of an element in the sample. The x-ray absorption coefficient is usually normalized to unit step height. This is done by regressing a line to the region before and after the absorption edge, subtracting the pre-edge line from the entire data set and dividing by the absorption step height, which is determined by the difference between the pre-edge and post-edge lines at the value of E0 (on the absorption edge). The normalized absorption spectra are often called XANES spectra.
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Q in cm−1) is variously called opacity, absorption coefficient, and attenuation coefficient. In nuclear physics, area cross-sections (e.g. σ in barns or units of 10−24 cm2), density mean free path (e.g. τ in grams/cm2), and its reciprocal the mass attenuation coefficient (e.g.
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Naturally, the origin (6), the datum circle (5), and the datum coordinate systems are virtual features which are imagined for mathematical purposes. The μ(x,y) is absorption coefficient of the object (3) at each (x,y), p(s,θ) (7) is the collection of fluoroscopic images.
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Using Terahertz for developing transmission images of packaged items. By using short THz pulses, a great variety of physical phenomena have already been studied. For unexcited, intrinsic semiconductors one can determine the complex permittivity or THz-absorption coefficient and refractive index, respectively.Grischkowsky, D.; Keiding, Søren; Exter, Martin van; Fattinger, Ch. (1990).
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An optical solar reflector (OSR) consists of a top layer made out of quartz, over a reflecting layer made of metal. OSRs are used for radiators on spacecraft. The quartz outer layer lets the solar light through which reflects on the metal layer. This results in a low absorption coefficient.
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That is, K_s/(K_s+K_a), where K_s is the scattering coefficient, and K_a is the absorption coefficient Single Scattering Albedo, scienceworld.wolfram.com. #h — The width of the opposition surge. #B_0 or S_0 — The strength of the opposition surge. #P_0 or g — The particle phase function parameter, also called the asymmetry factor.
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There are 520 amino acids in CFAP157 in human. The protein is glutamine extremely rich, and glycine poor. The protein is quite neutral with the isoelectric point at pH 7.4. The average mass of the protein is estimated to be 60,531.748 Da, and the absorption coefficient is estimated to be 25,440 M−1 cm−1.
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Intralipid is also widely used in optical experiments to simulate the scattering properties of biological tissues. Solutions of appropriate concentrations of intralipid can be prepared that closely mimic the response of human or animal tissue to light at wavelengths in the red and infrared ranges where tissue is highly scattering but has a rather low absorption coefficient.
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The incoherent propagation of light through the sheet can also be represented by a matrix. If no light redistribution takes occurs on the path, the propagation matrix D is a diagonal matrix. The single entries consist of the Lambert-Beer absorption factor, including cosine of the polar angle and the absorption coefficient of the respective material.
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A cover slip is glued onto the exposed surface. The adhesives, such as epoxy or Canada balsam resin, must have approximately the same refractive index (η ≈ 1.54) as glass. Most ceramics have a very small absorption coefficient (α ≈ 0.5 cm −1 for alumina in Fig. 2) in the Beer–Lambert law below, and can be viewed in transmitted light.
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Different types of electromagnetic radiation The total absorption coefficient of lead (atomic number 82) for gamma rays, plotted versus gamma energy, and the contributions by the three effects. Here, the photoelectric effect dominates at low energy. Above 5 MeV, pair production starts to dominate. Even though photons are electrically neutral, they can ionize atoms directly through the photoelectric effect and the Compton effect.
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This method is similar to the above method, however, the aperture is removed or enlarged to allow all the light to reach the detector. This in effect sets the normalized transmittance to S = 1. This is used in order to measure the non-linear absorption coefficient Δα. The main cause of non-linear absorption is due to two-photon absorption.
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Carrier concentrations and absorption coefficient of CZTS are similar to CIGS. Other properties such as carrier lifetime (and related diffusion length) are low (below 9 ns) for CZTS. This low carrier lifetime may be due to high density of active defects or recombination at grain boundaries. Many secondary phases are possible in quaternary compounds like CZTS and their presence can affect the solar cell performance.
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Single photon absorption is the earliest method to measure bone mineral density accurately. Its basic principle is that bone mineral density can be obtained by the law of absorption. In this law, the important parameters to be obtained are bone thickness, bone absorption coefficient and radiation intensity (or counting) after bone absorption. The thickness of soft tissue measured by single photon absorption method is the same.
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It is possible for dicofol to enter surface waters when soil erosion occurs. Breakdown in water: Dicofol degrades in water or when exposed to UV light at pH levels above 7. Its half-life in solution at pH 5 is 47 to 85 days. Because of its very high absorption coefficient (Koc), dicofol is expected to adsorb to sediment when released into open waters.
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He developed a method to carry out calculations of its transition probabilities. He calculated the photoelectric effect for hydrogen and X-rays, obtaining the absorption coefficient at the K-edge. His calculations accorded with observations of the X-ray absorption of the sun, but not helium. Years later it was realized that the sun was largely composed of hydrogen and that his calculations were indeed correct.
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For more information, please visit the links at the bottom of the page. We will solve the problem using an infinitely small point source (represented analytically as a Dirac delta function in space and time). Responses to arbitrary source geometries can be constructed using the method of Green's functions (or convolution, if enough spatial symmetry exists). The required parameters are the absorption coefficient, the scattering coefficient, and the scattering phase function.
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The first ones are termed visual distance moduli and are denoted by {(m - M)}_{v} while the second ones are called true distance moduli and denoted by {(m - M)}_{0}. Visual distance moduli are computed by calculating the difference between the observed apparent magnitude and some theoretical estimate of the absolute magnitude. True distance moduli require a further theoretical step, that is the estimation of the interstellar absorption coefficient.
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Metal halide perovskites possess unique features that make them useful for solar cell applications. The raw materials used, and the possible fabrication methods (such as various printing techniques) are both low cost. Their high absorption coefficient enables ultrathin films of around 500 nm to absorb the complete visible solar spectrum. These features combined result in the possibility to create low cost, high efficiency, thin, lightweight and flexible solar modules.
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This is because such specimens (being mostly water) have a low absorption coefficient at this wavelength. A low absorption is advisable so as to minimise damage to the biological material, sometimes referred to as opticution. Perhaps the most important consideration in optical tweezer design is the choice of the objective. A stable trap requires that the gradient force, which is dependent upon the numerical aperture (NA) of the objective, be greater than the scattering force.
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A large variety of medical applications (i.e. dermatology, dentistry) utilize erbium ion's emission (see Er:YAG laser), which is highly absorbed in water (absorption coefficient about ). Such shallow tissue deposition of laser energy is necessary for laser surgery, and the efficient production of steam for laser enamel ablation in dentistry. Erbium-doped optical silica-glass fibers are the active element in erbium-doped fiber amplifiers (EDFAs), which are widely used in optical communications.
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Brode graduated from Whitman College with his Bachelor of Science degree in 1921, and then entered the California Institute of Technology. He was awarded his Doctor of Philosophy (Ph.D.) in physics in 1924, the first year in which Caltech awarded this degree, for his thesis on "the absorption coefficient for slow electrons in gases". He showed that molecules with similar arrangements of their external electrons have similar cross sections for collisions with slow electrons.
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These calculations did not properly account for frequency-dependent attenuation of ultrasound in tissue or for the requirements of spectral unmixing.D. Razansky, J. Baeten, V. Ntziachristos, "Sensitivity of molecular target detection by multispectral optoacoustic tomography (MSOT)", Med. Phys. 36 (2009) 939-945. Experimental results suggest an in vivo detection sensitivity of 0.1-1 μM for organic dyes with a minimum detectable optical absorption coefficient of 0.1–1 cm−1, such as indocyanine green and Alexa fluochromes.
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At the receiver, the infrared signal strengths are measured by some form of infrared detector. Generally photodiode detectors are preferred, and are essential for the higher modulation frequencies, whereas slower photoconductive detectors may be required for longer wavelength regions. The signals are fed to low-noise amplifiers, then invariably subject to some form of digital signal processing. The absorption coefficient of the gas will vary across the passband, so the simple Beer–Lambert law cannot be applied directly.
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Fixed energy methods (FEXRAV) have been developed and applied to the study of the catalytic cycle for the oxygen evolution reaction on iridium oxide. FEXRAV consists of recording the absorption coefficient at a fixed energy while varying at will the electrode potential in an electrochemical cell during the course of an electrochemical reaction. It allows to obtain a rapid screening of several systems under different experimental conditions (e.g., nature of the electrolyte, potential window), preliminary to deeper XAS experiments.
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Gamma rays are photons, whose absorption cannot be described by LET. When a gamma quantum passes through matter, it may be absorbed in a single process (photoelectric effect, Compton effect or pair production), or it continues unchanged on its path. (Only in the case of the Compton effect, another gamma quantum of lower energy proceeds). Gamma ray absorption therefore obeys an exponential law (see Gamma rays); the absorption is described by the absorption coefficient or by the half-value thickness.
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The NIR window can be computed based on the absorption coefficient spectrum or the effective attenuation coefficient spectrum. A possible criterion for selecting the NIR window is given by the FWHM of the inverse of these spectra as shown in Figure 7. In addition to the total concentration of hemoglobin, the oxygen saturation will define the concentration of oxy and deoxyhemoglobin in tissue and so the total absorption spectrum. Depending on the type of tissue, we can consider different situations.
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The most important optical element in an isolator is the Faraday rotator. The characteristics that one looks for in a Faraday rotator optic include a high Verdet constant, low absorption coefficient, low non-linear refractive index and high damage threshold. Also, to prevent self-focusing and other thermal related effects, the optic should be as short as possible. The two most commonly used materials for the 700–1100 nm range are terbium doped borosilicate glass and terbium gallium garnet crystal (TGG).
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Tin(II) sulfide is an interesting potential candidate for next generation thin-film solar cells. Currently, both cadmium telluride and CIGS (copper indium gallium selenide) are used as p-type absorber layers, but they are formulated from toxic, scarce constituents. Tin(II) sulfide, by contrast, is formed from cheap, earth abundant elements, and is nontoxic. This material also has a high optical absorption coefficient, p-type conductivity, and a mid range direct band gap of 1.3-1.4 eV, required electronic properties for this type of absorber layer.
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THz spectroscopy can be used as a non-contact analytical method. The absorption coefficient and refractive index measured by terahertz pulsed spectroscopy can be used directly to obtain the high frequency-dependent complex conductivities of materials in the 0.1 – 3 THz (3 – 100 cm−1) region of the electromagnetic spectrum."Terahertz for Material Characterization" The technology has been applied to some areas of solid state physics research such as semiconductors, high-temperature superconductors, terahertz metamaterials, carrier density dynamics, graphene, carbon nanotubes, magnetism and more.
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The collimated transmission method is a direct way of measuring the optical properties of materials. It is especially useful for sensing the optical properties of tissues to guide developments of both diagnostic and therapeutic techniques. These optical properties are described by the absorption coefficient μa, scattering coefficient μs, and anisotropy factor g. In the collimated transmission method, a laser beam is directed perpendicularly to the material and the detection of reemitted light gives information about the total interactive effect of the optical properties of the material.
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Wallace Clement Sabine was the first scientist to study the sound-absorbing characteristics of materials in a scientifically rigorous manner. Paul Sabine, a distant cousin of Wallace, studied the repeatability of sound absorption coefficient measurements in reverberation chambers. Paul Sabine's work in the 1920s-1930s laid the groundwork for the ASTM C423 test methodology still used today. Prior to the development of a standard procedure for material testing or reverberation chamber construction, data at low frequencies was highly unreliable and differed significantly from manufacturer to manufacturer.
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Therefore, temperature stability has to be maintained while working with lead tin telluride based laser. However, the advantage is that the operating wavelength of the laser can simply be tuned by varying the operating temperature. The optical absorption coefficient of lead tin telluride is typically ~750 cm−1 as compared to ~50 cm−1 for the extrinsic semiconductors such as doped silicon. The higher optical coefficient value not only ensures higher sensitivity but also reduces the spacing required between individual detector elements to prevent optical cross talk making integrated circuit technology easily accessible.
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The production of heavy water was already under way in Norway when the Germans invaded on 9 April 1940. The Norwegian production facilities for heavy water were quickly secured (though some heavy water had already been removed) and improved by the Germans. The Allies and Norwegians had sabotaged Norwegian heavy water production and destroyed stocks of heavy water by 1943. Graphite (carbon) as an alternative was not considered as Walther Bothe's neutron absorption coefficient value for carbon was too high; probably due to the boron in the graphite pieces having high neutron absorption.
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The wavelength of laser diodes is tuned by means of temperature to produce an optimal compromise between the absorption coefficient in the crystal and energy efficiency (lowest possible pump photon energy). As waste energy is limited by the thermal lens this means higher power densities compared to high-intensity discharge lamps. High power lasers use a single crystal, but many laser diodes are arranged in strips (multiple diodes next to each other in one substrate) or stacks (stacks of substrates). This diode grid can be imaged onto the crystal by means of a lens.
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The optical cavity is formed by a period of λ/4 distributed Bragg reflector (DBR), made of non-absorbing larger bandgap materials, at the both end of the substrate. The front mirror has a transmittance of t1 and generally has lower reflectivity than compare to the mirror at back (R1 < R2 ). Transmittance t1 allows light to enter into the cavity, and reflectivity R1 (=r12) and R2 (=r22) provides the optical confinement in the cavity. The active region and the substrate region have absorption coefficient α and αex respectively.
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It is not possible to make any transition that lies within the energy or frequency range that is observed. The strength of an electromagnetic absorption process is mainly determined by two factors. First it is important to realize that transitions that only change the magnetic dipole moment of the system are much weaker than transitions that change the electric dipole moment and that transitions to higher order moments like quadrupole transitions are weaker than dipole transitions. Second, not all transitions have the same transition matrix element, absorption coefficient or oscillator strength.
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Milne moved on to consider the more realistic case where the strength of the absorption of light by gas within stars (expressed by the absorption coefficient) does vary with wavelength. Using simplifying assumptions he calculated how for the Sun the strength of the absorption depends on wavelength. His results could not be explained adequately at the time, but later negatively-charged hydrogen ions (H−) were shown to be a major contributor to Milne's results. Milne, working with Ralph H. Fowler, studied how the strengths of spectral lines of stars depend on their spectral type.
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In his thesis, Boyd described the effects of reflecting radiation through samples of powdered, cold-worked and annealed beryllium with differing particle sizes. The experiment showed that beryllium crystals are "rather imperfect", that annealing caused "no appreciable change" in beryllium's lattice structure, and that the mass absorption coefficient of beryllium found in the experiment was reasonably close to the theoretical value calculated using Compton's empirical formula. Boyd was appointed as head of the Mathematics and Science Department at West Georgia College in 1933. In 1935, he joined the faculty at the Georgia Institute of Technology as an assistant professor of physics.
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Soft tissue does not affect the results of bone tissue measurement. Therefore, the absorption coefficient of a beam of constant energy radiation can be calculated beforehand, and the intensity of radiation (or counting) can be obtained directly in patients' measurement. In the vertical C-frame, the collimated 125I light source (200 mCi or 74 GBq) and the collimated NaI (TI) scintillation detector-photomultiplier tube are mounted in relative geometric shapes to place the measured body parts between the source and the detector. The source and detector assembly are rigidly connected and driven by a motor to cross the longitudinal axis of the bone.
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Because the material has a high absorption coefficient and strongly absorbs sunlight, a much thinner film is required than of other semiconductor materials. CIGS is one of three mainstream thin-film photovoltaic (PV) technologies, the other two being cadmium telluride and amorphous silicon. Like these materials, CIGS layers are thin enough to be flexible, allowing them to be deposited on flexible substrates. However, as all of these technologies normally use high- temperature deposition techniques, the best performance normally comes from cells deposited on glass, even though advances in low-temperature deposition of CIGS cells have erased much of this performance difference.
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CdS is used optionally and some CIGS cells contain no cadmium at all.Solar-Frontier.com CIS Advantages CIGS has an exceptionally high absorption coefficient of more than 105/cm for 1.5 eV and higher energy photons. CIGS solar cells with efficiencies around 20% have been claimed by the National Renewable Energy Laboratory (NREL), the Swiss Federal Laboratories for Materials Science and Technology (Empa), and the German Zentrum für Sonnenenergie und Wasserstoff Forschung (ZSW) (translated: Center for Solar Energy and Hydrogen Research), which is the record to date for any thin film solar cell.ZSW: Press Releases. Zsw-bw.de.
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He first identified the 4050 group of lines observed in comets as being due to the C3 molecule. Using a method that he developed, Douglas made the first studies of the Zeeman effect in polyatomic molecules. According to Gerhard Herzberg: > One of Douglas' most important contributions was his recognition of the > reason for "anomalous lifetimes," that is, the failure of a simple > relationship between absorption coefficient and lifetime to account for > lifetimes in such compounds as NO2, SO2, C6H6. This phenomenon, referred to > in the most recent literature as the Douglas effect, is closely connected > with internal conversion in larger molecules.
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In electron energy loss spectroscopy, Kramers–Kronig analysis allows one to calculate the energy dependence of both real and imaginary parts of a specimen's light optical permittivity, together with other optical properties such as the absorption coefficient and reflectivity. In short, by measuring the number of high energy (e.g. 200 keV) electrons which lose a given amount of energy in traversing a very thin specimen (single scattering approximation), one can calculate the imaginary part of permittivity at that energy. Using this data with Kramers–Kronig analysis, one can calculate the real part of permittivity (as a function of energy) as well.
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The core holes thus created can then be filled by nonradiative decay of a higher-lying electron and communication of energy to yet another electron, which can then escape from the surface (Auger emission). The photoabsorption can therefore be monitored by direct detection of these Auger electrons to the total photoelectron yield. The absorption coefficient versus incident photon energy contains oscillations which are due to the interference of the backscattered Auger electrons with the outward propagating waves. The period of this oscillations depends on the type of the backscattering atom and its distance from the central atom.
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An X-ray filter is a material placed in front of an X-ray source in order to reduce the intensity of particular wavelengths from its spectrum and selectively alter the distribution of X-ray wavelengths within a given beam. When X-rays hit matter, part of the incoming beam is transmitted through the material and part of it is absorbed by the material. The amount absorbed is dependent on the material's mass absorption coefficient and tends to decrease for incident photons of greater energy. True absorption occurs when X-rays of sufficient energy cause electron energy level transitions in the atoms of the absorbing material.
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Futterman (1962) p.5280 :K(iw) =k(w)+ i a(w) \quad (1.3) Here a(w) is taken positive to assure that energy is lost from the wave to the medium. Now when K(w) are separated into a real part for attenuation and an imaginary part for dispersion, we can introduce the Kramer-Krönig relation by a Hilbert transform H of the attenuation a(w): :K(iw) = H(a(w))+ i a(w) \quad (1.4) For our calculations to be valid we must make two assumptions: (a) the absorption coefficient a(w) is strictly linear in the frequency, over the range of measurement. We can call it bw.
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Since the focusing power of this weak nonlinear lens depends on the nonlinear refractive index, it would be possible to extract its value by analyzing the z-dependent data acquired by the detector and by cautiously interpreting them using an appropriate theory. To measure the imaginary part of the nonlinear refractive index, or the nonlinear absorption coefficient, the z-scan setup is used in its open-aperture form. In open- aperture measurements, the far-field aperture is removed and the whole signal is measured by the detector. By measuring the whole signal, the beam small distortions become insignificant and the z-dependent signal variation is due to the nonlinear absorption entirely.
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This method is based on the integrating plate technique, in which the change in optical transmission of a filter caused by particle deposition is related to the light absorption coefficient of the deposited particles using Beer- Lambert's Law. One of the instruments used to characterize the amount and composition of bioaerosols was the Wideband Integrated Bioaerosol Sensors (WIBS). This instrument uses ultraviolet light-induced fluorescence (UV-LIF) to detect the fluorescence signals from common amino acids like tryptophan and nicotinamide adenine dinucleotide (NADH). A lamp flashing the gas xenon is able to detect particle’s size and shape using high precision ultraviolet wavebands (280nm and 370nm).
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In absorption spectroscopy of cylindrical flames or plumes, the forward Abel transform is the integrated absorbance along a ray with closest distance y from the center of the flame, while the inverse Abel transform gives the local absorption coefficient at a distance r from the center. Abel transform is limited to applications with axially symmetric geometries. For more general asymmetrical cases, more general-oriented reconstruction algorithms such as algebraic reconstruction technique (ART), maximum likelihood expectation maximization (MLEM), filtered back-brojection (FBP) algorithms should be employed. In recent years, the inverse Abel transform (and its variants) has become the cornerstone of data analysis in photofragment-ion imaging and photoelectron imaging.
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The ejected photoelectron interacts with electrons in the surrounding non-excited atoms. If the ejected photoelectron is taken to have a wave-like nature and the surrounding atoms are described as point scatterers, it is possible to imagine the backscattered electron waves interfering with the forward-propagating waves. The resulting interference pattern shows up as a modulation of the measured absorption coefficient, thereby causing the oscillation in the EXAFS spectra. A simplified plane-wave single-scattering theory has been used for interpretation of EXAFS spectra for many years, although modern methods (like FEFF, GNXAS) have shown that curved-wave corrections and multiple-scattering effects can not be neglected.
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Biological tissues are diffusive media, which means that light attenuation during propagation is due not only to absorption, but also to scattering. The former is related to the chemical composition of the medium and induces photon annihilation, whereas the latter depends on the microscopic inhomogeneities of its refractive index and determines deviations in photon's trajectory. The absorption coefficient \mu_a represents the probability per unit length that an absorption event takes place, while the scattering coefficient \mu_s denotes the probability per unit length that a scattering event occurs. However, many studies refer to the reduced scattering coefficient \mu_s^'=\mu_s (1-g) rather than the simple scattering coefficient, in order to take into account the medium's anisotropy.
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Schematic of a typical SPV apparatus Surface photovoltage measurements are performed by placing a wafer or sheet film of a semiconducting material on a ground electrode and positioning a kelvin probe a small distance above the sample. The surface is illuminated with light whose wavelength is scanned using a monochromator so as to vary the absorption depth of the photons. The deeper in the semiconductor that carrier generation occurs, the fewer the number of minority carriers that will reach the surface and the smaller the photovoltage. On a semiconductor whose spectral absorption coefficient is known, the minority carrier diffusion length can in principle be extracted from a measurement of photovoltage versus wavelength.
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Schematic of a z-scan setup In nonlinear optics z-scan technique is used to measure the non-linear index n2 (Kerr nonlinearity) and the non-linear absorption coefficient Δα via the "closed" and "open" methods, respectively. As nonlinear absorption can affect the measurement of the non-linear index, the open method is typically used in conjunction with the closed method to correct the calculated value. For measuring the real part of the nonlinear refractive index, the z-scan setup is used in its closed-aperture form. In this form, since the nonlinear material reacts like a weak z-dependent lens, the far-field aperture makes it possible to detect the small beam distortions in the original beam.
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Arranging the room surfaces (including the ceiling) to be non-parallel helps inhibit the formation of standing waves - additional acoustic diffusers are often used to create more reflecting surfaces and further encourage even distribution of any particular sound field. Reverberation chambers are used in acoustics as well as in electrodynamics, such as for measurement microphone calibration, measurement of the sound power of a source, and measurement of the absorption coefficient of a material. All these techniques assume the sound field in the chamber to be diffuse, and will normally use a broadband sound source (e.g. white noise or pink noise) so that the resulting sound field contains acoustic energy across the whole audible range.
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Beer-Lambert Relationship Plot Many substances absorb light in the ultraviolet - visible light range. Absorption at any particular wavelength in the ultraviolet visible range is proportional to the concentration of the substances in the solution or other medium, in accord with the Beer-Lambert relationship. In a practical sense, the Beer-Lambert relationship can be stated as: A = ε x l x c in which A is the absorbance measured by the instrument, ε is the molar absorption coefficient of the sample, l is the pathlength of the light beam through the sample, and c is the concentration of the substance in the solution or medium. The Spectronic 20 is thereby commonly used for quantitative determination of the concentration of a substance of interest.
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For instance, the diffuse attenuation coefficient of downwelling irradiance, Kd (it is often used as an index of water clarity or ocean turbidity) is defined as an AOP, while the absorption coefficient and the scattering coefficient of the medium are defined as IOPS. There are two different approaches to determine the concentration of optically active water components by the study of the spectra. The first approach consist of empirical algorithms based on statistical relationships and the second approach consists of analytical algorithms based on the inversion of calibrated bio-optical models. Accurate calibration of the relationships/models used is an important condition for successful inversion on water remote sensing techniques and the determination of concentration of water quality parameters from observed spectral remote sensing data.
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The second meaning of dichroic refers to the property of a material, in which light in different polarization states traveling through it experiences a different absorption coefficient; this is also known as diattenuation. When the polarization states in question are right and left-handed circular polarization, it is then known as circular dichroism. Since the left- and right-handed circular polarizations represent two spin angular momentum (SAM) states, in this case for a photon, this dichroism can also be thought of as Spin Angular Momentum Dichroism. In some crystals,, such as Tourmaline, the strength of the dichroic effect varies strongly with the wavelength of the light, making them appear to have different colours when viewed with light having differing polarizations.
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Particle-induced gamma emission (PIGE) is a form of nuclear reaction analysis, one of the ion beam analysis thin-film analytical techniques. Typically, an MeV proton beam is directed onto a sample which may be tens of microns thick, and the fast protons may excite the target nuclei such that gamma rays are emitted. These may be used to characterise the sample. For example, sodium in glass is of great importance but can be hard to measure non destructively: X-ray fluorescence (XRF) and particle-induced X-ray emission (PIXE) are both sensitive only to the surface few microns of the sample because of the low energy (and consequent high absorption coefficient) of the Na K X-rays (1.05 keV).
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440x440px Extended X-Ray Absorption Fine Structure (EXAFS), along with X-ray Absorption Near Edge Structure (XANES), is a subset of X-ray Absorption Spectroscopy (XAS). Like other absorption spectroscopies, XAS techniques follow Beer's law. The X-ray absorption coefficient of a material as a function of energy is obtained using X-rays of a narrow energy resolution are directed at a sample and the incident and transmitted x-ray intensity is recorded as the incident x-ray energy is incremented. When the incident x-ray energy matches the binding energy of an electron of an atom within the sample, the number of x-rays absorbed by the sample increases dramatically, causing a drop in the transmitted x-ray intensity.
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