Showing papers on "Absorption (electromagnetic radiation) published in 1974"
01 Jan 1974
TL;DR: In this paper, the use of the compressional hydromagnetic mode (also called the magnetosonic or simply, the fast wave) is examined in some detail with respect to the heating of a tritium plasma containing a few percent deuterium.
Abstract: The use of the compressional hydromagnetic mode (also called the magnetosonic or, simply, the fast wave) is examined in some detail with respect to the heating of a tritium plasma containing a few percent deuterium. Efficient absorption of wave energy by the deuteron component is found when ω = ωC (deuterons), with Qwave 100. Reasonable efficiencies are found also for electron heating, but coherence effects between transit-time and Landau damping for electrons reduce the total absorption for both processes to one-half of the transit-time power, calculated separately.The fusion output of a two-component neutral-injected plasma can be enhanced by selective heating of the injected deuterons. Also, selective deuteron absorption may be used for ion-tail creation by radiofrequency excitation alone, as an alternative to neutral injection. The dominant behaviour of the high-energy deuteron distribution function is found to be f(v) ~ exp[(3/2)∫vdv / ], where is the Chandrasekhar-Spitzer drag coefficient, and is the Kennel-Engelmann quasi-linear diffusion coefficient for wave-particle interaction at the deuteron cyclotron frequency. An analytic solution to the one-dimensional Fokker-Planck equation, with r.f.-induced diffusion, is developed, and using this solution together with Duane's fit to the D-T fusion cross-section, it is found that the nuclear-fusion power output from an r.f.-produced two-component plasma can significantly exceed the incremental (radiofrequency) power input.
557 citations
TL;DR: In this article, the optical effect of the substrate on the anomalous absorption of aggregated silver films is taken into account in terms of the dipole interaction between an island particle and its mirror image in the substrate.
326 citations
TL;DR: In this article, a new detector for the measurement of energy by total absorption, based on the use of multiple-plate ion chambers, is described, which allows absolute calibration and very good gain stability.
232 citations
TL;DR: In this paper, a cw difference-frequency spectrometer was developed for the 2.2 to 4.2 μm infrared region by mixing argon and tunable dye lasers in LiNbO3.
Abstract: A cw difference-frequency spectrometer has been developed for the 2.2 to 4.2 μm infrared region by mixing argon and tunable dye lasers in LiNbO3. A resolution of 5 × 10−4 cm−1 with continuous scans up to 1 cm−1 and a scan precision better than 2 × 10−3 cm−1 have been achieved. Tunable ir powers of ~1 μW have been obtained, enabling sensitive absorption measurements and real-time spectroscopy. The range, resolution, speed, and sensitivity of this difference-frequency technique are demonstrated by absorption traces of water vapor, ammonia, methane, and nitrous oxide.
230 citations
TL;DR: In this paper, a series of high-quality silica glasses doped with 0.01 to 0.1 wt% of each transition element (V through Cu) was prepared by a vapor hydrolysis technique.
Abstract: The optical absorption of 3d transition elements in fused silica was studied. A series of high-quality silica glasses doped with 0.01 to 0.1 wt% of each transition element (V through Cu) was prepared by a vapor hydrolysis technique. Their optical spectra were measured, and their practical absorptivities were calculated between 200 and 2000 nm. In the proposed waveguide use range (∼ 850 nm), V and Cr appear to absorb most (apract= 2.6 and 1.2 dB/km ppbw−1 (metal), respectively) and Cu the least (apract≃0). Comparisons are made with data for conventional glasses.
207 citations
193 citations
TL;DR: The results suggest that phosphorylation in Chlorella can be driven by an electrical potential only, in agreement with formal results obtained in spinach chloroplasts and with the electrochromic hypothesis of Witt et al.
185 citations
01 Jan 1974
TL;DR: A radioisotope method to measure iron absorption from the whole diet was used in this article, which is based on the concept that food iron is absorbed from two pools, the heme iron pool and the nonheme pool, which can be especially labeled with two radioiron isotopes given as hemoglobin and as an iron salt.
Abstract: A new radioisotope method to measure iron absorption from the whole diet was used in this study. The method is based on the concept that food iron is absorbed from two pools, the heme iron pool and the nonheme iron pool, which can be especially labeled with two radioiron isotopes given as hemoglobin and as an iron salt. The purpose of this study was to test the accuracy of this two-pool extrinsic tag method. The meals served were composed as an average of 6 wk consumption in the present material of 32 young enlisted men. The mean and total heme and nonheme iron absorption in all the 32 young men was 1.01+/-0.11. This figure agrees well with the mean daily losses expected for this group of subjects (1.0 mg). The conclusion can therefore be made that there are no major systematic errors of the present method to measure the total iron absorption from a mixed diet. In one series a comparison was made of the absorption of heme and nonheme iron from the meals. A significant correlation between the absorption of the two kinds of iron was found. However, a much greater fraction of the heme iron was absorbed (37%) than of the nonheme iron (5%). The absorption both from breakfast and lunch was in two series found to give a good prediction of the total daily nonheme iron absorption. One series was designed to compare the effect of two levels of iron fortification. There was a significant increase in iron absorption when the level of iron fortification of the meals was increased.
182 citations
TL;DR: In this paper, the ultraviolet spectra of SiO2 and high-purity silicate glasses were analyzed in the wavelength region extending from 90 to 350 nm, and the effects of network modifiers, impurity-induced absorption, luminescence and radiation damage, both permanent and transient, were discussed.
Abstract: Ultraviolet spectroscopy is a useful experimental tool for the determination of the electronic structure of glasses. This paper discusses the ultraviolet spectra of SiO2 and high-purity silicate glasses. It considers in turn, absorption intrinsic to the SiO network, the effects of network modifiers, impurity-induced absorption, luminescence and radiation damage, both permanent and transient, in the wavelength region extending from 90 to 350 nm.
172 citations
TL;DR: The spectral dependence of the fundamental absorption edge of congruently grown undoped LiNbO3 has been measured from 10 to 667 K as mentioned in this paper, where the edge is broad and featureless and showed very little dichroism.
Abstract: The spectral dependence of the fundamental absorption edge of congruently grown undoped LiNbO3 has been measured from 10 to 667 K. Similar measurements on stoichiometric samples were made at 80 and 300 K. In all cases at all temperatures the edge is broad and featureless and showed very little dichroism (<0.01 eV). The spectral dependence of the absorption is exponential at high temperatures but not at low temperatures. Possible models to explain the observed shapes are discussed.
TL;DR: In this article, the optical constants of dry films of deoxyribonucleic acid (sodium salt of calf thymus DNA) have been determined in the 2 −82 eV region of photon energy.
Abstract: Optical constants of dry films of deoxyribonucleic acid (sodium salt of calf thymus DNA) have been determined in the 2–82 eV region of photon energy. The extinction coefficient k was obtained by transmission measurements on thin films on metal mesh screens. The refractive index n in the nonabsorbing region 2–4 eV was obtained from critical‐angle measurements on films deposited on a sapphire semicylinder. To determine the value of n above 4 eV, a Kramers‐Kronig analysis was performed using the measured values of k. From these optical constants the complex dielectric function e and the energy‐loss function for charged particles −Im(1/e) were derived. The results exhibit, in addition to the well‐established absorptions around 4.7 and 6.5 eV, a strong absorption at 13.8 eV and a prominent peak in the energy‐loss function at 21.6 eV which exhibits a large degree of collective behavior.
TL;DR: A comparison study on the relationship between the amount of bran added and the decrease in iron absorption in patients with high iron sensitivity finds that bran addition is associated with lower iron absorption.
Abstract: Bran is known to reduce iron absorption. There is, however, no information on the relationship between the amount of bran added and the decrease in iron absorption. In the present study a comparison w
TL;DR: In this paper, it was shown that the absorption currents in polymers (mainly polyethylene terephthalate) are consistent with the Walden model of injection, followed by build up of trapped space charge.
Abstract: It is shown that published experimental data on absorption currents in polymers (mainly polyethylene terephthalate) are consistent with the Walden model of injection, followed by build up of trapped space charge. The published results do not agree with the tunnelling process, dipolar relaxation or electrode polarisation. Detailed analysis indicates that the injection efficiency rises sharply with field, and that the observed current-time plots arise from the change in field at the injecting electrode, rather than from a modification of the barrier shape. It follows that the knee in the current-time plot does not reflect a transit time, but is a measure of t0, a complex function of field and injection mechanism. It also follows that the steady-state currents are controlled by the transport mechanism in the bulk.
TL;DR: In this paper, a set of experimental data concerning the giant dipole resonance of nuclei (GDR) in the 103 ≦ A ≦ 133 mass region was presented, and it was shown that the width of the GDR increases as β increases and as E 2+ decreases and that theoretically predicted spreading of the dipole strength is confirmed by their experimental results.
TL;DR: In a variety of amorphous materials, the far infrared and microwave absorption (3-3000 GHz or 0.1-100 cm−1) is orders of magnitude greater than that observed in corresponding crystalline materials as mentioned in this paper.
TL;DR: In this paper, a configuration interaction wavefunctions have been used to evaluate absorption oscillator strengths, using both the length and velocity forms, for transitions between the 1s22s2p and 1s 22p2p states: 3P0 to 3Pe; 1P 0 to 1De, 1P0-1Se; and 1P 1S to 1S. The results showed that the length values stabilize fairly quickly while the corresponding velocity values are more sensitive.
Abstract: Configuration interaction wavefunctions have been used to evaluate absorption oscillator strengths, using both the length and velocity forms, for transitions between the 1s22s2p and 1s22p2 states: 3P0 to 3Pe; 1P0 to 1De; 1P0 to 1Se. It is found that the length values stabilize fairly quickly while the corresponding velocity values are more sensitive. Both L-shell and K-L inter-shell correlations are considered. The latter make small changes to length values, but alter velocity values by up to 10%. All-external configurations are important for neutral beryllium and to some extent for B II also. The 1s22p2 1S state of neutral beryllium appears to be about 0.01 a.u. above the Be+ 2s threshold. The calculations of Burke (1972) for the 1s22s2 1S to 1s22s2p1P0 transition are extended, and compared with the accurate calculations of Sims and Whitten (1973). Agreement to within 2% is achieved.
Patent•
16 Aug 1974
TL;DR: Optically pumped laser amplifiers are discussed in this article, where a broad band of absorption transitions and energy levels corresponding to at least one fluorescent emission transition are relaxed by non-radiating transitions.
Abstract: Optically pumped laser amplifiers are disclosed. One type of such amplifier utilizes an excitable medium, the atoms, ions or molecules of said medium having well defined energy states including a lowest state, a lower state above said lowest state, and a higher state above said lower state, and a bright pumping light source composed of a radiative substance different from such medium which radiative substance emits energy in a spectral range which can be absorbed by such medium, and wherein the major portion of the energy absorbed by such medium causes transitions of the atoms, ions, or molecules thereof to populate the higher state. Another type of such amplifier utilizes a medium of atoms, ions, or molecules, some of which have broad bands of energy levels corresponding to a broad band of absorption transitions and energy levels corresponding to at least one fluorescent emission transition, the upper energy levels of said broad bands being above the upper level of said fluorescent emission transition, and wherein some of the upper energy levels above the upper level of said fluorescent emission transition are rapidly quenched via non-radiating transitions to the upper level of said fluorescent emission transition. In a preferred embodiment of the latter amplifier, the lower energy level corresponding to the fluorescent emission transition is relaxed by non-radiating transitions.
TL;DR: In this article, the production processes and spatial distribution of fast ions resulting from tangential injection of a diffuse neutral beam into a tokamak are discussed and calculated and discussed in detail.
Abstract: The production processes and spatial distribution of fast ions resulting from tangential injection of a diffuse neutral beam into a tokamak are discussed. The spatial distribution of fast ions for various injection trajectories and absorption mean free paths are calculated and discussed in detail. Maximum beam absorption for a parabolic density profile is shown to occur for injection roughly halfway between the inner wall of the torus and the magnetic axis; however, since this maximum is near unity and only weakly dependent on the injection trajectory, this is not the most important possible optimization. Since the drift orbit surface area over which the fast ions are distributed is roughly proportional to the distance from the magnetic axis, the fast ion density is found to be strongly peaked at the magnetic axis for present experiments where the absorption mean free path λ is comparable to the plasma radius a. This geometric peaking effect is strong enough to overcome the exponential beam attenuation and cause the fast-ion density and consequent beam energy deposition to be peaked at the plasma centre as long as λ0 a/4. Charge exchange of the fast ions with neutrals in the plasma can deplete the fast-ion population, particularly near the plasma edge. When charge exchange is an important loss mechanism, beam injection nearly tangent to the magnetic axis is found to maximize the beam effectiveness in heating.
TL;DR: In this article, an extra absorption band with two peaks is observed at the low energy region of the absorption edge for Fe-doped CuAlS 2 and CuGaS 2, respectively.
Abstract: Optical absorptions have been measured in chalcopyrite, CuFeS 2 , and Fe-doped CuAlS 2 and CuGaS 2 An extra absorption band with two peaks is observed at the low energy region of the absorption edge for Fe-doped CuAlS 2 and CuGaS 2 Energy positions of two absorption peaks are 13 eV and 20 eV for CuAlS 2 and 12 eV and 19 eV for CuGaS 2 , respectively The intensity of this absorption band increases with the increase of doped Fe ions and grows into the absorption edge of CuFeS 2 Its oscillator strength comes up to 7·10 -2 In chalcopyrite photoconductivity is observed and its maximum is just at the same energy region of the absorption edge By comparing our results with those of absorption measurements for Cu- or Fe-doped ZnS it is concluded that this absorption band originates from the charge transfer transitions relating to 3d electron of Fe ions and the absorption edge of CuFeS 2 rises from the band-to-band transition corresponding to this charge transfer transition
TL;DR: In this paper, the absorption of light by surface plasmons has been studied using the method of attenuated total reflection, and the reflectance from a quartz-Ag interface has been measured as a function of angle and surface structure for the wavelength region from 3600 to 6000.
TL;DR: In this paper, the authors examined the absorption of microwaves by the human skull by making computerized calculations of theoretical models of the skull and compared the calculated relative absorption versus frequency for homogeneous and inhomogeneous skull models.
Abstract: Resonance absorption of microwaves by the human skull is examined by making computerized calculations of theoretical models of the skull. The calculated relative absorption versus frequency is plotted and compared for homogeneous and inhomogeneous skull models. At a frequency of maximum power absorption, the spatial distribution of intracranial field intensity (based upon the theoretical model) is also calculated and plotted.
TL;DR: A laser absorption spectrometer, using an ir laser transmitter and a heterodyne radiometer, can be used from an aircraft or spacecraft to measure altitude profiles of air pollutants and other atmospheric constituents.
Abstract: A laser absorption spectrometer, using an IR laser transmitter and a heterodyne radiometer, can be used from an aircraft or spacecraft to measure altitude profiles of air pollutants and other atmospheric constituents. The technique involves measurement of differential absorption at several wavelengths, using the diffusely reflecting earth's surface to provide a return signal. The pressure broadening of absorption lines allows one to discriminate between high and low altitude absorbers. Application of the technique to measurements of ozone, nitric oxide, and water vapor are presented. CO2 and CO lasers are considered as transmitters. The discussion includes altitude resolution limitations, atmospheric temperature dependence, and frequency stability requirements of the instrument.
TL;DR: In this paper, the spectrum has been divided into 19 wavelength intervals and opacity distribution functions have been constructed for each interval, and the atmospheric photodissociation rates of O2, O3, CO2, H2O, HO2, NO2 and HNO3 are presented.
TL;DR: In this article, the absorption of microwaves in a normally magnetized YIG disk has been measured and analyzed, and the absorption peaks are interpreted to be caused by magnetostatic waves propagating radially across the disk.
Abstract: The absorption of microwaves in a normally magnetized YIG disk has been measured and analyzed. The absorption peaks are interpreted to be caused by magnetostatic waves propagating radially across the disk. The mode numbers of absorption peaks are determined by the aspect ratio of the disk, (ω/γ)2−Hi2 and BiHi −(ω/γ)2, where ω is the microwave angular frequency, γ is the gyromagnetic ratio, and Hi and Bi are internal magnetic fields and depend upon the applied magnetic field. The experimental values of the applied magnetic field at which the absorption peaks are caused are in good agreement with the theoretical values. It has been verified both theoretically and experimentally that the new mode absorptions due to the magnetostatic waves exist in the case of ω/γ−[Bi(0)Hi(0)]1/2 =dH > 0, where Bi(0) and Hi(0) are the internal fields at the disk center. These new mode abosrption peaks tend to shift toward the cutoff point of the usual absorption spectra as the incident microwave power is increased.
TL;DR: The average deposition velocity for SO 2 over the British Isles is likely to be about 0·8 cm s −1 (referred to concentrations measured 20 cm above the surface) as discussed by the authors.
TL;DR: In this paper, the authors compared the absorption and fluorescence spectra of Er3+ in germanate and tellurite glasses using the Judd-Ofelt theory and intensity parameters obtained from measured intergrated absorption coefficients.
Abstract: Absorption and fluorescence spectra of Er3+ in germanate and tellurite glasses were obtained. Spontaneous transition probabilities of the 4 S 3 2 and 4 F 9 2 to all terminal levels of Er3+ were calculated using the Judd-Ofelt theory and intensity parameters obtained from measured intergrated absorption coefficients. Quantum efficiencies of the 4 S 3 2 and 4 F 9 2 fluorescences were measured by the comparative method and by the use of measured decay times. Multiphonon relaxation rates for 4 S 3 2 → 4 F 9 2 and 4 F 9 2 → 4 I 9 2 were calculated using the experimental data. The average rate for 4 S 3 2 → 4 F 9 2 in germanate is 1.16 × 105 sec−1 and in tellurite is 1.60 × 104 sec−1, and the rate for 4 F 9 2 → 4 I 9 2 is 2.85 × 10 5 sec −1 in germanate and 2.33 × 105 sec−1 in tellurite. The higher rates in germanate glasses are explained by the stronger interaction of the glass phonons with the electronic states of Er3+ in germanate than in tellurite glasses. This also explains the higher quantum yield of the visible fluorescence of Er3+ in tellurite glasses compared to other glasses.
TL;DR: In this article, the roles played by thermal and radiative transport in the propagation of LSC waves were investigated in 19 frequency groups, the flux of each being calculated from the temperature in discrete cells along the LSC wave axis and allowed to deposit in other cells according to temperature dependent absorption coefficients for air.
Abstract: We report results of an investigation into the roles played by thermal and radiative transport in the propagation of Laser Supported Combustion (LSC) waves We replace the volume radiation losses assumed by Raizer with detailed treatment of radiation in 19 frequency groups, the flux of each being calculated from the temperature in discrete cells along the LSC wave axis and allowed to deposit in other cells according to temperature dependent absorption coefficients for air Calculations of LSC wave structure and propagation velocity as a function of laser intensity are compatible with available experimental data a = c = CP = f = h = h = hi(a) = K = k = KV =