Showing papers on "Absorption (electromagnetic radiation) published in 1969"
TL;DR: In this article, the spectral absorption coefficient and the total emissivities of soot suspensions were calculated for the room temperature optiaI.1 and 2.5-1O.
Abstract: Data on the room temperature optiaI.1 constants of soot are presentedfor the 'Wavelength regions 0.4-().8j.1 and 2.5-1O.0j.l. Dispersion formulas are developedfor interpolating the data between0.8 and 2.5j.1. The results are used to calculate the spectral absorption coefficient and the total emissivities of soot suspensions. It is shown that the correct values of the optiaI.l constants are neededin the use of light-scattering techniques for the measurement of the soot concentration but that uncertainties introduced in flux
746 citations
TL;DR: In this article, absorption measurements of spherical silver particles suspended as colloid in photosensitive glasses were performed and it was shown that the absorption coefficient at the wavelength of absorption peak (λ = 0.405 μ) remains constant, whereas the refractive index increases by about a factor of 5 when the particle size decreases.
Abstract: By evaluating, with help of Mie's theory, absorption measurements of spherical silver particles — (between 24 and 210 A in diameter) — suspended as colloid in photosensitive glasses we found that the absorption coefficient at the wavelength of absorption peak (λ=0.405 μ) remains constant, whereas the refractive index increases by about a factor of 5 when the particle size decreases. Within accuracy of measurements and the differences of bulk optical constants of various authors this deviation from the bulk values can be described by the “free path effect”, the influence of conduction electron collisions with particle surfaces. The results are compared with the quantum mechanical theory ofKawabata andKubo.
594 citations
TL;DR: Absorption in air and plastic of 20-eV to 50,000- eV monoenergetic electron beams was studied to study the effect of ionization on absorption in air.
Abstract: Absorption in air and plastic of 20-eV to 50,000-eV monoenergetic electron beams was studied. A cylindrical ionization chamber operated at 10-3 to 250 torr was used to measure absorption in air. Th...
225 citations
TL;DR: In this paper, the authors show that the singular behavior of conduction electrons can be understood in terms of density waves of the conduction electron which are excited when, in the absorption process, the core hole is created.
Abstract: Singularities near the threshold of the soft x-ray spectra of metals have been predicted by Mahan and have recently been calculated by Nozi\`eres et al. using the model of a localized core hole. We show that the singular behavior can be understood in terms of density waves of the conduction electrons which are excited when, in the absorption process, the core hole is created, providing an attractive potential for the conduction electrons. For the description of the conduction electrons in terms of density waves, Tomonaga's model is adopted.
213 citations
TL;DR: PAH transport was studied using isolated, perfused rabbit proximal renal tubules and it was concluded that PAH is actively transported into the tubule cell at the peritubular membrane and subsequently diffuses into the luminal fluid.
Abstract: TUNE,BRUCE M., MAURICE B. BURG,AND CLIFFORD SPATLAK. Charac~eri.ctics uf p-aminohippurata transport in proximal renal tubules. Am. J. Physiol. 217(4): 1057-1063. I969,-PAH transport was studied using isolated, perfused rabbit proximal renal tubules. ,4ctive PAH secretion was found in both the convoluted and the straight portion of the proximal tubule, but the rate of secretion was approximately 3 times as great in the straight portion. During perfusion, PAH concentration was greater in tubule cells than in luminal fluid or surrounding bath. When tubules were incubated without perfusion, PAH concentration in tubule cells was higher than during perfusion and was greater in the straight than in the convoluted portion. It is concluded that PAH is actively transported into the tubule cell at the peritubular membrane and subsequently diffuses into the luminal fluid. On the basis of this model, the permeabilities of the luminal and peritubular cell membranes to PAH were calculated. Passive PAH absorption from the tubular lumen was studied, and both the rate of efflux and tissue concentration of PAH were in agreement with the predictions made from the model. Changes in perfusion rate from 3 to 10 nl min --I had no measurable effect on the PAH secretion rate.
191 citations
TL;DR: In this article, the shape of the extreme wings of self-broadened CO2 lines was investigated in three spectral regions near 7000, 3800, and 2400 cm−1, where much of the absorption by samples at a few atm is due to strong lines of strong lines whose centers occur below the band heads.
Abstract: The shapes of the extreme wings of self-broadened CO2 lines have been investigated in three spectral regions near 7000, 3800, and 2400 cm−1. Absorption measurements have been made on the high-wavenumber sides of band heads where much of the absorption by samples at a few atm is due to the extreme wings of strong lines whose centers occur below the band heads. New information has been obtained about the shapes of self-broadened CO2 lines as well as CO2 lines broadened by N2, O2, Ar, He, and H2. Beyond a few cm−1 from the line centers, all of the lines absorb less than Lorentz-shaped lines having the same half-widths. The deviation from the Lorentz shape decreases with increasing wavenumber, from one of the three spectral regions to the next. The absorption by the wings of H2- and He-broadened lines is particularly low, and the absorption decreases with increasing temperature at a rate faster than predicted by existing theories.
185 citations
TL;DR: In this article, the effect is treated within a simple model by the methods of perturbation theory and it is shown that even to lowest order one must sum the parquet diagrams, in close analogy with the Abrikosov theory of the Kondo effect.
Abstract: X-ray emission and absorption spectra in metals may display singularities near the Fermi-level threshold. These singularities, predicted by Mahan, are due to final-state interactions between conduction electrons and the localized disturbance created by the x ray. The effect is treated within a simple model by the methods of perturbation theory. It is shown that even to lowest order one must sum the so-called parquet diagrams, in close analogy with the Abrikosov theory of the Kondo effect. Mahan's prediction is confirmed, and its validity discussed. Various secondary effects which could blur the singularity are analyzed.
180 citations
TL;DR: A fitting inquiry was made into metabolic determinants which might render susceptible some of the exposed workers susceptible to manganism, which argues that the bulk of the inhaled manganese becomes transferred into the gastrointestinal tract, from which it is either absorbed or eliminated.
Abstract: MANY MINEHS are exposed to manganese dusts, but few develop chronic manganism. Those who do (develop manganism) exhibit a selflimited psychiatric disorder, at the end of which neurological manifestations emerge.1-2 These manifestations persist after the excess metal acquired at work becomes cleared from the tissues.3 This low but unpredictable propensity suggests that the victims of manganism are being selected among exposed miners by some unusual factors which permit flooding of the brain with intolerable amounts of metal. These factors could conceivably bc genetic or industrial, but our patient population is too small for the application of genetic or epidemiologic techniques. A fitting inquiry was made into metabolic determinants which might render susceptible o d y some of the exposed workers. The lung has long been thought of as the cardinal portal of entry for the offending metal.‘ The evidence discussed below argues, however, that the bulk of the inhaled manganese becomes transferred into the gastrointestinal tract, from which it is either absorbed or eliminated;5 hence this canal must be a portal of entry, even for manganese which is first inhaled. Investigations of the intestinal absorption of manganese are complicated by the fact that absorption and reexcretion of this metal proceed almost concurrently.5 In the intact man, ingestion of a manganese tracer alone cannot permit the differentiation between fractions headed for elimination and those headed for absorption. The use of an additional marker
179 citations
175 citations
TL;DR: In this paper, the N2 Vegard-Kaplan system has been observed in the absorption spectrum of 12 m·atm of gas and the electronic transition moment has been calculated from the measured transition probabilities and extrapolated with the aid of emission measurements.
Abstract: Seven bands (6, 0–12, 0), of the N2 Vegard–Kaplan system have been observed in the absorption spectrum of 12 m·atm of gas. The measuring instrument was a 2‐m scanning spectrometer with a resolution of about 30 000. Pulse‐counting techniques, coupled with the use of a theoretical model based on a measured collision broadening coefficient, have allowed fairly accurate estimates of the transition probabilities of the observed bands. The electronic transition moment has been calculated from the measured transition probabilities and extrapolated with the aid of emission measurements, in order to determine the lifetimes of the system. It is shown that the system has a double lifetime for each vibrational level. The calculated lifetimes [τi(υ′)] for the A 3Σu+ (υ = 0) state were τ2(0) = 1.27 sec for the Σ = 0 substate levels, and τ1(0) = τ3(0) = 2.5 sec for the Σ = 1, −1 substate levels.
166 citations
TL;DR: In this paper, the rotational and vibrational band structure of carbon monoxide absorption in vacuum UV region was discussed, and the fourth positive CO system was observed in absorption of vacuum UV regions.
Abstract: Fourth positive carbon monoxide system observed in absorption in vacuum UV region, discussing rotational and vibrational band structure
TL;DR: In this paper, the authors derived the hole diffusion length for Te-doped GaAs with electron concentrations ranging from 2×1016 to 6.5×1018 cm−3.
Abstract: Hole diffusion lengths L were determined for several Te‐doped GaAs crystals with electron concentrations ranging from 2×1016 to 6.5×1018 cm−3. The values of L were obtained by fitting experimental photoluminescence spectra to a theoretical expression which contains the measured absorption coefficients. This expression was derived from radiative recombination statistics, taking into account the reabsorption of emitted photons and the diffusion of minority carriers. The idea used by van Roosbroeck and Shockley of introducing the measured absorption coefficient by means of the principle of detailed balance is shown here to be valid for both nondegenerate and degenerate n‐type GaAs. It was found that the hole diffusion lengths are nearly independent of electron concentration n for n 2×1018 cm−3 values for diffusion length decrease rapidly with increasing n. This decrease is attributed to the formation of additional defects associated with donor complexes or precipitates, or both. The diffusion lengths determined in this work are in good agreement with those found by Wittry and Kyser from the electron‐beam excitation method but are larger than those obtained by Aukerman et al. from short‐circuit current measurements on n‐type surface barrier diodes subjected to high‐energy electron bombardment.
TL;DR: In this article, the optical properties of seven liquid metals, in the frequency range between 0·77 and 5·0 ev and at temperatures up to 1600°c, were measured by a polarimetric method.
Abstract: Measurements have been made, by a polarimetric method, of the optical properties of seven liquid metals, in the frequency range between 0·77 and 5·0 ev and at temperatures up to 1600°c. For Al the results show no sign of the absorption peak at about 1·5 ev which is observed for the solid and are in rough agreement with the Drude free-electron curves; deviations from these curves may be due to surface contamination, though an attempt to explain them quantitatively in this way is not successful. For Cu, Ag and Au the results at low frequencies suggest that the effective density of conduction electrons, n∗, rises slightly on melting, as is to be expected if the structure of the conduction band is smoothed out; the absorption edges due to excitation of electrons from the d band, however, are scarcely changed at all. For the transition metals Fe, Co and Ni, which lie next to one another in the Periodic Table, the absorption spectra show little in the way of structure; the most notable feature of the r...
TL;DR: In this paper, the authors measured the energy gap at the fundamental absorption edge of HgTe over the composition range 0.23 to 0.61 and at temperatures from 300° to 10°K.
Abstract: The absorption coefficient at the fundamental absorption edge has been measured in Hg1−xCdxTe over the composition range 0.23≤x≤0.61 and at temperatures from 300° to 10°K. The energy gap, estimated from the position of the absorption edge, increases continuously with increasing CdTe content but was not linear between the values for HgTe and CdTe. The energy gap of the alloys varied approximately linearly with temperature for T>100°K, going from a positive temperature coefficient for x 0.5. The temperature coefficient of the gap, dEg/dT, was linear with composition and extrapolated to +5.6×10−4 eV/°K for HgTe. The expression Eg(x, T)=−0.303+1.73x+5.6×10−4(1−2x)T+0.25x4 was obtained from the data and can be used to obtain the energy gap as a function of x and T over a large range of these variables.
TL;DR: Comparative studies of the availability of food iron are best carried out against a reference standard in the same subject, and intrasubject variations can be reduced by multiple dose administration.
TL;DR: Using the continuous spectrum of synchrotron radiation, the absolute absorption coefficient of seven transition metals has been determined in the spectral range 40-300eV as discussed by the authors, where the strong oscillations reported by previous investigators appear to have been spurious.
TL;DR: The current status of absorption cross-section measurements for aeronomic use is reviewed in this article, where the recommended values for the gases O2, N2, O, and O3 are given at wavelengths where there is a strong atmosphere.
Abstract: The current status of absorption cross-section measurements for aeronomic use is reviewed. Recommended values for the gases O2, N2, O, and O3 are given at wavelengths where there is strong atmosphe...
TL;DR: In this article, a method for investigation of the surface layers composition and structure is described, using the conversion electrons emitted after recoilles absorption of gamma-rays, which depends on the thickness of the layer the electrons pass across.
TL;DR: In this article, the absorption of laser radiation by an inhomogeneous overdense plasma has been investigated, and it was shown that the expansion preferentially takes place normal to the film which is in agreement with observation.
Abstract: Calculations of the absorption of laser radiation by an inhomogeneous overdense plasma have been carried out. Such a plasma is produced when a high‐powered laser irradiates a solid particle. Nearly complete absorption is found as long as 2R is greater than c⊥ here, R is the scale length for density falloff, c is the velocity of light, and ⊥ is the electron‐ion collision time for a plasma frequency equal to the incident laser frequency. For hydrogen this gives complete absorption up to temperatures of 5 keV if R is greater than 5 × 10−2 cm; higher Z materials absorb better. The expansion of a laser‐produced plasma was also investigated. In the case of a plasma produced from a thin metallic film, it is found that the expansion preferentially takes place normal to the film which is in agreement with observation.
TL;DR: Jupiter spectrum observations in 2.8-14 micron range, describing absorption strength and brightness temperature, basing analysis on ammonia, methane and hydrogen absorption as discussed by the authors, were used for the analysis.
Abstract: Jupiter spectrum observations in 2.8-14 micron range, describing absorption strength and brightness temperature, basing analysis on ammonia, methane and hydrogen absorption
TL;DR: The effect of plastic deformation on the optical absorption, ESR, and thermoluminescent properties of MgO has been investigated in this article, where plastische deformation produces an optical absorption band at about 217 nm whose intensity is proportional to the percent of deformation.
Abstract: The effect of plastic deformation on the optical absorption, ESR, and thermoluminescent properties of MgO has been investigated. Plastic deformation produces an optical absorption band at about 217 nm whose intensity is proportional to the percent of deformation. No new ESR signals were detected in the deformed crystals. When deformed crystals are irradiated with 60CO γ-rays, however, the ESR signal from the F-center is observed and several new optical absorption bands also appear. Impurity ion ESR signals in γ-irradiated samples have been compared with thermoluminescence spectra. The results indicate that the blue thermoluminescence at 3.3 eV and 85°C is due to Fe2+ converting to Fe3+ and the red thermoluminescence at 1.7 eV and 85°C is due to the formation of Cr3+.
Es wird der Einflus einer plastischen Verformung auf die optische Absorption, ESR und thermische Lumineszenz von MgO untersucht. Die plastische Deformation erzeugt optische Absorption bei 217 nm, deren Starke direkt proportional zur Verformung ist. In den verformten Kristallen wurden keine neuen ESR-Signale gefunden. Jedoch wurden ESR-Signale von F-Zentren und verschiedene neue optische Bander beobachtet, wenn die deformierten Kristalle γ-bestrahlt wurden. Die ESR-Signale von Fremdionen in den γ-bestrahlten Proben wurden mit den thermischen Lumineszenzspektren verglichen. Die Ergebnisse weisen darauf hin, das die blaue Lumineszenz bei 3,3 eV und 85°C beim Ubergang von Fe2+ in Fe3+ und die rote bei 1,7 eV und 85°C bei der Bildung von Cr3+ entsteht.
Patent•
16 Apr 1969TL;DR: In this article, a GaAs infrared emitting diode coated with a phosphor for converting this emission to visible light is shown to have increased light output, due to certain design modifications.
Abstract: Increased light output results from certain design modifications in a GaAs infrared emitting diode coated with a phosphor for converting this emission to visible light. These design modifications include shape and dimensional considerations for minimizing internal reflection and absorption of infrared emission within the diode as well as dimensional and compositional considerations as applied to the coating for reducing scattering losses and minimizing internal reflection of its emission.
TL;DR: In this paper, the properties of isolated carbon and carbon-oxygen complexes have been studied in silicon containing various carbon isotopes and the strength of the local mode absorption has been confirmed.