Showing papers on "Radiative transfer published in 1970"
TL;DR: In this article, a set of new inverse problems is formulated for the determination of the concentration of absorbing gases in an atmosphere, the extent and height of clouds, and surface elevations.
Abstract: It is shown that the relaxation method for inverse solution of the full radiative transfer equation leads to unique temperature profiles. Apart from its attractive simplicity, the algorithm is also capable of discriminating between noise and valid information without any need for data smoothing. A set of new inverse problems is formulated for the determination of the concentration of absorbing gases in an atmosphere, the extent and height of clouds, and surface elevations. The proposed methods are illustrated by examples in the earth's atmosphere for the region of the 4.3 μ CO2 band.
280 citations
TL;DR: An iterative solution is developed for the temperature and absorbing gas profiles of an atmosphere from spectral and angular measurements of atmospheric radiance, novel in that there is no limiting assumption made about the analytical form of the profile imposed by the number of radiance observations available.
Abstract: An iterative solution is developed for the temperature and absorbing gas profiles of an atmosphere from spectral and angular measurements of atmospheric radiance. This iterative solution is novel in that there is no limiting assumption made about the analytical form of the profile imposed by the number of radiance observations available. The solution is demonstrated through the determination of temperature and water vapor profiles of the earth's atmosphere from Nimbus III and Nimbus IV Satellite InfraRed Spectrometer (SIRS) observations. The solutions are compared with conventional rawinsonde and rocket-sonde observations. The results indicate that this solution can be used effectively to specify the general meteorological characteristics of an atmosphere from satellite or ground-based radiometric observations.
154 citations
TL;DR: Radiative heat flux between two parallel copper disks at cryogenic temperature, showing dependence on emitter temperature and spacing as discussed by the authors, showing that the radii flux depends on the number of parallel disks.
Abstract: Radiative heat flux between two parallel copper disks at cryogenic temperature, showing dependence on emitter temperature and spacing
133 citations
114 citations
TL;DR: In this paper, the M, N 1, N 2 and N 3 emission bands were found near the band edge in CuCl single crystal with excitation by the two-photon absorption of a Q-switched ruby laser.
Abstract: New emission bands called the M , N 1 , N 2 and N 3 bands have been found near the band edge in CuCl single crystal with excitation by the two-photon absorption of a Q -switched ruby laser. All emission intensities show non-linear dependences upon the excitation intensity. One of them, the M band located at λ3919 A at 4.2°K, is concluded as the radiative decay of a free excitonic molecule. The shape variation and peak shift to the low energy side of the M emission band with respect to the increase of the laser power are similar to those due to the raising of temperature. The line shape is an inverted replica of the Maxwell distribution. The system of the excitonic molecule has been concluded to have the effective temperature which is higher than the lattice temperature in the high density state of excitonic molecule. The mechanism of the radiative decomposition of the excitonic molecule has been discussed.
107 citations
TL;DR: In this paper, the problem of diffuse reflection, transmission and emission of infrared radiation by water clouds is investigated in the wavelength region from 5-50 µm, where the drop-size distribution is assumed to be that of altostratus measured by Diem.
Abstract: The problem of diffuse reflection, transmission and emission of infrared radiation by water clouds is investigated in the wavelength region from 5–50 μ. The drop-size distribution of clouds is assumed to be that of altostratus measured by Diem. The phase function and other optical properties of the clouds are estimated from the value of the refractive index of water proposed by Pontier and Dechambenoy. Radiative processes due to both cloud droplets and water vapor in the cloud are taken into account, and a method of averaging the solution over a spectral interval including a number of absorption lines is developed.
103 citations
TL;DR: In this article, the authors considered the possibility that white light flares are due to heating of the photosphere by a flux of energetic ions and electrons impinging on it from above.
Abstract: We consider the possibility that white light flares are due to heating of the photosphere by a flux of energetic ions and electrons impinging on it from above. Particles with energy in the range 10 MeV to 1 BeV release most of their energy to the ambient gas at about optical depth unity in the photosphere. This increase in energy produces a temperature perturbation of several hundred degrees in the layer and results in a re-radiation of the energy with a radiative relaxation time of several seconds. The consequences of this model are applied to a study of the great flare of May 23, 1967 and to the very fast event of August 11, 1954. Large numbers of very energetic electrons or protons must be produced in the first few minutes of the primary flare event if our interpretation (or one based on synchrotron emission) is correct.
93 citations
TL;DR: In this paper, the authors investigated the effect of heavy-atom effects on radiative and non-radiative singlet-triplet transitions in aromatic hydrocarbons and concluded that the effect is due to mixing of excited singlet states associated with the perturber molecule into the triplet state of the perturbed molecule.
Abstract: The nature of the external heavy‐atom effect on radiative and nonradiative singlet–triplet transitions in aromatic hydrocarbons has been investigated experimentally and theoretically. From studies of the perturbed phosphorescence of aromatic hydrocarbons in rigid glass and mixed‐crystal systems we conclude that:(i) Radiative T1 ↔ S0 transitions are much more susceptible to a heavy‐atom effect than are the corresponding radiationless transitions.(ii) The enhancement of the radiative T1 ↔ S0 transitions is due to mixing of excited singlet states associated with the perturber molecule into the triplet state of the perturbed molecule.(iii) The important pertuber states appear to be highly localized on the heavy atom rather than states which are essentially delocalized [e.g., (π, π*) states].(iv) It does not seem necessary to invoke charge‐transfer interactions to account for the enhancement.
81 citations
TL;DR: Similarity representation of the radiative gas dynamic equations with spherical symmetry, amenable to a wide variety of radiation law, is presented in this article, where a simple artifice of retaining the definitions of the radiant quantities as operators on radiative intensity and recognizing the variability of the index refraction is employed.
Abstract: Similarity representation of the radiative gas dynamic equations with spherical symmetry, amenable to a wide variety of radiation law, is presented. The general representation of the equations of motion is effected by the simple artifice of retaining the definitions of the radiant quantities as operators on the radiative intensity and of recognizing the variability of the index refraction. Specific constitutive forms for the radiation field manifest themselves in implied constraint conditions. Because of radiative heating, similarity structure may be prescribed for the gas on both sides of shock waves. Numerical examples are constructed for strong explosions and implosions.
70 citations
TL;DR: In this paper, an invariant imbedding approach was used to solve the equations of radiative transfer by solving the convexity of the radiational transfer problem, and the solution was shown to be invariant.
Abstract: This thesis is a study of the solutions of the equations of radiative transfer by an invariant imbedding approach.
62 citations
TL;DR: In this paper, the authors reviewed recent experimental work and its theoretical interpretation concerned with the density effect on the energy loss of charged particles in matter with particular reference to electrons and muons and concluded that such an effect has not been substantiated experimentally, and that the predicted radiative corrections are likely to be small.
Abstract: Recent experimental work and its theoretical interpretation concerned with the density effect on the energy loss of charged particles in matter is reviewed with particular reference to electrons and muons. Recent proposals that radiative corrections should result in a significant reduction in the ionization loss at very high energies are analyzed in some detail. It is concluded that such an effect has not been substantiated experimentally, and that the predicted radiative corrections are likely to be small (\ensuremath{\sim}1%).
TL;DR: In this article, the visible emission from electronically excited NO2 has been studied both with thermal excitation in an electric oven and with recombination excitation from the nitric oxide-atomic oxygen reaction.
Abstract: The visible emission from electronically excited NO2 has been studied both with thermal excitation in an electric oven and with recombination excitation from the nitric oxide–atomic oxygen reaction. In both cases the emission is continuous with weaker, diffuse bands superimposed. The correlation of these bands with NO2 absorption bands has been extended. The thermal emission continuum begins near 3300 A and increases in intensity to the end of our range at 8600 A. The recombination emission continuum begins near 3800 A and has a broad maximum at 6200 A, in general agreement with previous workers. The absolute intensity of the thermal emission has been obtained at 100‐A intervals between 4600 and 8600 A for temperatures between 972 and 1335°K. Excitation energies, which are obtained from the variation of intensity with temperature, range from 66 kcal at 4600 A to a minimum of 44 ± 1 kcal near 8300 A. This latter value is E0, the minimum energy of the emitting state of NO2. Radiative lifetimes are obtained ...
TL;DR: In this article, the atomic oxygen emission at 63 μ was analyzed between 50 km and 250 km for several atmospheric models and the frequency integrated intensities and the volume emission rates were computed and discussed in connection with experimental and theoretical investigations of atomic oxygen distribution.
TL;DR: Magnetic field effects on phosphorescence intensity and lifetime of isolated naphthalene molecules at 1.6°K were investigated in this article, where in addition to the decay times of the individual spin components it is possible to separate the radiative and radiationless parts of the decay.
TL;DR: In this article, effective beta-decay coupling constants G′v and G′A are defined which include renomalizing effects due to the electromagnetic interaction, and it is concluded that only those theories of electromagnetic radiative corrections which take account of a very heavy intermediate vector boson are able to reconcile the values of g′v, Gμ and the Cabibbo angle determined from polar vector strangeness changing semi-leptonie decays.
TL;DR: In this article, a radiative lifetime study of the K2 B 1 Πu molecule excited by the 632.8nm line of an He-Ne laser was performed.
Abstract: Using the phase‐shift method, a radiative lifetime study has been made of the K2 B 1Πu molecule excited by the 632.8‐nm line of an He–Ne laser. The radiative lifetime extrapolated to zero pressure is found to be τ = 12.4 ± 0.3 nsec where the error represents three standard deviations of the statistical uncertainty. A simple valence‐bond model for the molecular transition is proposed which predicts that the radiative lifetime of the B 1Πu state of the dialkalis will be shorter, by about a factor of 2 or more, than the lifetime of the parent atomic P state into which the excited alkali dimer separates. The results of these calculations are compared with the experimentally observed lifetimes for several vibrational states of Na2 and K2.
Journal Article•
TL;DR: In this article, the outer, model-independent, radiative corrections to allowed nuclear β-decay are evaluated for all Z in the multiplicative approximation, and results are presented in graphical and tabular form.
TL;DR: In this paper, the effect of stimulated Raman excitation of the v = 1 J = 1 level of normal H 2 has been studied at 300°K by optical scattering techniques.
TL;DR: Radiative transfer equation for spectral line formed in multidimensional atmosphere, solving for two dimensional atmospheric model as discussed by the authors, solved for two-dimensional atmospheric model and solving for 2D atmospheric model.
Abstract: Radiative transfer equation for spectral line formed in multidimensional atmosphere, solving for two dimensional atmospheric model
TL;DR: In this paper, the density of excited atoms and the diffusely reemitted radiation were calculated for a homogeneous radiation field incident on a slab using the solutions of the Biberman-Holstein integral equation.
Abstract: The density of excited atoms and the diffusely reemitted radiation is calculated for a homogeneous radiation field incident on a slab. The solutions of the Biberman-Holstein integral equation are used in the calculations. The optical thickness is assumed to be large. The line shapes of both the absorption line and the incident radiation are arbitrary.
TL;DR: In this article, a large number of T(r, I)-distributions measured in a 5 mm ON2 cascade arc at normal pressure are used to evaluate the transport properties of nitrogen up to 26,000 °K.
Abstract: TheE(I)-characteristic and a large number ofT(r, I)-distributions measured in a 5 mm ON2 cascade arc at normal pressure are used to evaluate the transport properties of nitrogen up to 26,000 °K. The electrical conductivityσ(T) and from this the cross-section for atom-electron collision and the Coulomb-cross-section are determined directly from theE(I)- and severalT(r, I)-curves. For the evaluation of the thermal conductivityκ(T) three temperature regions are discerned: Up to about 10,000 °Kκ(T) is derived directly from the energy equation since here the energy transport by radiation does not play an important role. Between 10,000 and 15,000 °K the radiative energy flux for different arc currents, the thermal conductivity and from this the charge exchange cross-section are determined in a good approximation utilizing the large number of measured temperature distributions. Above 15,000 °K the already evaluated collision cross-sections are used to computeκ(T). Withκ(T) known the radial distribution of the balance between emission and absorption of radiative power per unit volume is evaluated for different arc currents. It turns out, that at the highest measured arc current, i.e. 570 A, in the axial region of the arc about 95% of the supplied energy is carried off by radiation.
TL;DR: In this article, a macroscopic equation of radiative transfer for the multi-level system is obtained by summation of the microscopic equation, specialized to a harmonic-oscillator rigid-rotor molecule, over all rotational and vibrational transitions.
Abstract: Macroscopic equations are formulated for the nonequilibrium interaction of radiative and vibrational rate processes in an infrared-active diatomic gas. Radiative transitions are taken into account initially in a microscopic formulation for a general two-level system, with line broadening included. The macroscopic equation of radiative transfer for the multi-level system is then obtained by summation of the microscopic equation, specialized to a harmonic-oscillator rigid-rotor molecule, over all rotational and vibrational transitions. The resulting transfer equation is necessarily coupled to the vibrational rate equation, which is formulated heuristically on the basis of energy-exchange mechanisms and the established model for collisional relaxation. The entire development is influenced by its intended application in radiative gas dynamics. Such application is illustrated in its simplest form by the development of the corresponding acoustic theory.
TL;DR: In this article, the rate of excitation of the O(33S) term in an aurora from observed intensity profiles was derived from radiative transfer calculations appropriate to optically thick media in the presence of molecular absorption.
TL;DR: The observed elongation of the radiative fluorescence lifetimes and the temperature dependence of the radative transitions in the case of all trans retinol is interpreted as being due to the fact that only the lowest vibrorotational sublevels of 1S1, have a reasonable radiative transition probability.
Abstract: — The radiative fluorescence lifetimes of the all-trans, 9 cis and 13 cis retinol, have been measured at various temperatures, and in various solvents. The comparison of these results and of the data calculated from the absorption spectra using the Strickler and Berg equation shows that the transition probabilities are at least one hundred times lower for the radiative emission than for the absorption. Such a discrepancy, which is a general property of the polyenic structure, is closely related to the magnitude of the shift between absorption and fluorescence spectra. We interpret the observed elongation of the radiative fluorescence lifetimes and the temperature dependence of the radiative transitions in the case of all trans retinol as being due to the fact that only the lowest vibrorotational sublevels of 1S1, have a reasonable radiative transition probability: the temperature dependence of the radiationless transitions is considered to be due to the existence of a non radiative decay pathway at 550cal/mole above the ‘0’ level.
TL;DR: In this paper, the surface plasmons are excited in this experiment by light, and a relatively accurate determination of the optical constants is possible by using gold and silver foils of different thicknesses.
Abstract: Non radiative surface plasmons decay into photons on a rough surface. This light emission is studied with gold- and silver foils of different thicknesses. The surface plasmons are excited in this experiment by light. By this way a relatively accurate determination of the optical constants is possible.
TL;DR: The radiative corrections of order Zα 2 to pure Fermi decays have been studied in detail in this paper, and the result is applied to the experimentally accessible pure fermi decay.
TL;DR: Minerals radiative thermal conductivity at high temperatures from IR measurement of absorption coefficient and refractive index was analyzed in this paper, showing that the absorption coefficient is positively correlated with the refractive indices.
Abstract: Minerals radiative thermal conductivity at high temperatures from IR measurement of absorption coefficient and refractive index