Showing papers on "Debye published in 1975"
TL;DR: In this article, a simulation of the absorption process for radiation of energy density E20/4πnT ranging from much less than to somewhat greater than unity has been performed, showing that the appearance of a finite density variation over the distance of a few Debye lengths is forced by strong gradients in the plasma wave intensity and electron temperature.
Abstract: Resonant absorption has been simulated for radiation of energy density E20/4πnT ranging from much less than to somewhat greater than unity. Characteristic features of the absorption process are an absorption efficiency of approximately 50%, generation of suprathermal particles, and strong modification of the density profile in the vicinity of the critical density. The latter effect, the appearance of a finite density variation over the distance of a few Debye lengths, is forced by strong gradients in the plasma wave intensity and electron temperature. Such a density discontinuity greatly enhances the range of incidence angles for which resonance absorption is effective and decreases the effects of the oscillating two‐stream and ion‐acoustic decay instabilities.
240 citations
01 Sep 1975
TL;DR: In this article, a review of studies of the electric-field environment of the moon is given, and the electric fields, which are approximated by the surface potential over the Debye length, are shown to be at least three orders of magnitude higher than the pervasive solar-wind electric field and to be confined to within a few tens of meters of the lunar surface.
Abstract: A review is given of studies of the electric-field environment of the moon. Surface electric potentials are reported for the dayside and terminator regions, electron and ion densities in the plasma sheath adjacent to each surface-potential regime are evaluated, and the corresponding Debye lengths are estimated. The electric fields, which are approximated by the surface potential over the Debye length, are shown to be at least three orders of magnitude higher than the pervasive solar-wind electric field and to be confined to within a few tens of meters of the lunar surface.
114 citations
TL;DR: In this paper, the effect of parent phase ordering in depressing the T 0 temperature has been satisfactorily explained using a quasichemical approach and a consequent difference in bonding enthalpies.
99 citations
TL;DR: In this article, the theory of Debye and Bueche for the frictional properties of dilute polymer solutions is placed on a microscopic basis and a variational principle of minimum energy dissipation is formulated which is suitable for numerical work.
Abstract: The theory of Debye and Bueche for the frictional properties of dilute polymer solutions is placed on a microscopic basis. It is shown that the microscopic foundations for the theories of Debye−Bueche and Kirkwood−Riseman are identical, but that the theories differ in their statistical analysis. The Debye−Bueche equations are applied to the rotational friction coefficient of a spherically symmetric polymer with arbitrary radial density distribution. An exact result is derived for a Gaussian distribution of low density. A variational principle of minimum energy dissipation is formulated which is suitable for numerical work.
95 citations
TL;DR: In this paper, a new series of heat capacity measurements over the temperature range 1.2-40°K, for four chalcopyrites, give ΘD values at 0'°K.
Abstract: Values of crystalline‐solid Debye temperatures depend both on the method and temperature of measurement. Simple relationships between Debye temperatures and such cohesive properties as compressibility and melting point were derived over 60 years ago by Madelung, by Einstein, and by Lindemann. Debye temperatures ΘXR of a number of piezoelectric semiconductors with chalcopyrite structure have been determined at room temperature by x‐ray diffraction. A new series of heat capacity measurements over the temperature range 1.2–40 °K, for four chalcopyrites, give ΘD values at 0 °K. A common proportionality is found between each of these ΘXR and ΘD values and microhardness, and also melting point: Acceptable reproducibility is given for the AIBIIICVI2 chalcopyrites and, separately, the AIIBIVCV2 compounds. Values of Θ are predicted for 15 additional chalcopyrites. Excellent proportionality between Θelastic and compressibility is found for the europium chalcogenides, based on the data of Shapira and Reed.
94 citations
TL;DR: The interpretation of the temperature dependence of dielectric loss peaks in many materials is carried out implicitly within the framework of the Debye mechanism as discussed by the authors, which cannot produce a good physical insight into the situation and here I look at it from a new standpoint.
Abstract: ALTHOUGH the dielectric loss peaks in many materials are known to show a frequency dependence which departs radically from the ideal Debye shape, the interpretation of their temperature dependence is carried out implicitly within the framework of the Debye mechanism. This cannot produce a good physical insight into the situation and here I look at it from a new standpoint.
81 citations
TL;DR: In this article, the effect of long range Coulomb and dipolar forces on the collective tumbling of rigid linear dipoles is considered, and explicit expressions for these relaxation times are derived for polar and electrolyte solutions.
Abstract: The effect of long range Coulomb and dipolar forces on the collective tumbling of rigid linear dipoles is considered. It is shown that the Debye relaxation times are modified by the presence of these long range forces in important ways. Explicit expressions for these relaxation times are derived for polar and electrolyte solutions. It is shwon that for dense solutions there are significant deviations from the Debye semicircle in the Cole−Cole plot.
60 citations
TL;DR: In this article, Raman and infrared band shapes of some symmetric top molecules in the neat liquid and in solution were measured and used to obtain vibrational and rotational correlation functions and relaxation times.
59 citations
TL;DR: Scalar Debye potentials for neutrino, electromagnet, and gravitational perturbations of space-times were derived by extending the Hertzian zero-rest-mass field potentials of Penrose to curved spaces.
57 citations
TL;DR: In this article, it was shown that the 9-8 P(13) line of the 12C16O laser (1884.349 cm−1) has been used to study laser Stark Lamb dip spectra associated with the R(3/2) line in the rotation-vibration fundamental band of NO.
Abstract: The 9–8 P(13) line of the 12C16O laser (1884.349 cm−1) has been used to study laser Stark Lamb dip spectra associated with the R(3/2) line of the rotation–vibration fundamental band of NO. We have observed fully resolved hyperfine structure (line width ≈ 500 kHz) due to both components, Ω = 3/2 and 1/2, of the 2Π ground state. In addition, two level crossing signals have been observed in the v = 1 vibrational state of the 2Π1/2 component. The values we obtain for the electric dipole moment (in Debye) are:It was possible to determine μ′ and μ″ separately for the 2Π1/2 component because of the observation of the level crossing signals, which depend only on μ′. Our result for μ″ of 2Π1/2 agrees, within error limits, with a more precise previous measurement by molecular beam techniques, and our other results are more precise than previous determinations based on infrared intensities.
55 citations
TL;DR: An asymmetric distribution of relaxation times has been inferred from an increase in the Cole-Cole distribution parameter α with increasing values of ωτ in 62% v 2 O 5 −38% P 2 O 2 glass as mentioned in this paper.
TL;DR: In this paper, the conductivity of a dilute solution of ionized salt can be calculated if the equivalent conductance of the individual ions at infinite dilution and their valence states are known.
Abstract: 204 RESEARCH pendent means of checking analyses minimizes this possibility. An opportunity for such an independent check is provided by a comparison of the measured conductivity with a value calculated from the analyses. The conductivity of a dilute solution of ionized salt can be calculated if the equivalent conductance of the individual ions at infinite dilution and their valence states are known. The formula was developed by Kohlrausch, empirically, and later theoretically verified by Debye, Huckel, and Onsager. This equation can be written as
TL;DR: In this article, the rotational constants of the slightly asymmetric rotor H14N3 in the microwave and millimeter wave regions were measured for both a-and a-type Q-branch rotational transitions.
TL;DR: In this article, a lumped capacitance method for measurement of the permittivity and conductivity of materials in the radio and microwave frequency ranges is presented, and the analysis of the method applicable in both frequency and time domains is given for materials having low frequency conductivity or Debye dispersion.
Abstract: Further discussion of a lumped capacitance method for measurement of the permittivity and conductivity of materials in the radio and microwave frequency ranges is presented. The analysis of the method applicable in both frequency and time domains is given for materials having low frequency conductivity or Debye dispersion.
TL;DR: In this article, the bound-bound and bound-free transition strengths for a particle bound by a screened Coulomb (Debye) potential were investigated and shown that near the ionization limit transition strengths differ markedly from hydrogenic values: oscillator strengths of Rydberg series diminish more rapidly than the hydrogenic n-3 decrement and photoionization cross sections are zero at threshold.
Abstract: Computations of bound-bound and bound-free transition strengths for a particle bound by a screened Coulomb (Debye) potential show that near the ionization limit transition strengths differ markedly from hydrogenic values: oscillator strengths of Rydberg series diminish more rapidly than the hydrogenic n-3 decrement and photoionization cross sections are zero at threshold. Sharp near-threshold photoionization resonances occur for appropriate Debye lengths. This paper examines these effects and presents illustrative computations.
TL;DR: In this article, the microwave spectrum of thiane, a heterocyclic analog of cyclohexane, has been studied in the region 26.5-40 GHz.
TL;DR: In this paper, the critical voltage effect of high-voltage electron diffraction has been used to measure the X-ray Debye temperatures of Cr, α-Fe and their disordered alloys.
Abstract: The critical-voltage effect of high-voltage electron diffraction has been used to measure the X-ray Debye temperatures of Cr, α-Fe and their disordered alloys. The 220 critical voltages were measured at room and elevated temperatures for the pure metals and at room temperature for five intermediate compositions. The data for the pure metals were sufficient to determine both the Debye temperature and the deviation from the free-atom value of the atomic scattering factor at the first-order reflection position. The results agree with those of other workers. The scattering factor deviations were assumed to be the same in the alloys as in the pure metals, and this made it possible to determine the alloy Debye temperatures from a single room-temperature measurement of the critical voltage at each intermediate composition. The Debye temperatures are analyzed successfully in terms of a simple one-parameter theory, and are correlated with the alloy melting-point data through Lindemann's formula.
TL;DR: In this article, the size effect in the vibrational specific heat of small metallic particles is discussed and the size dependence of the maxima in specific heat enhancement is investigated for free boundaries.
TL;DR: Level crossings between hyperfine levels were observed in the nonlinear absorption of CD 3 I ν 2 Q P(4,1) transition by using the P(16) laser line of the CO 2 10.6 μm band as mentioned in this paper.
TL;DR: In this paper, a new empirical method of averaging the shear modulus is proposed, which is in good agreement with the observed polycrystalline data, and the elastic Debye temperatures ϑ calculated for a number of cubic elements and semiconducting compounds have been found to be in excellent agreement with corresponding computationally exact ϑ.
Abstract: A new empirical method of averaging the shear modulus is proposed. The elastic Debye temperatures ϑ calculated for a number of cubic elements and semiconducting compounds have been found to be in excellent agreement with the corresponding computationally exact ϑ. The computed shear modulus is also in good agreement with the observed polycrystalline data.
TL;DR: In this article, the transfer impedance between two small dipole antennae, each much shorter than a Debye length, separated by a distance of ten or more Debye lengths, was measured.
Abstract: We show theoretically that the electron density and temperature of a plasma could be deduced from the measurements of the transfer impedance between two small dipole antennae, each much shorter than a Debye length, separated by a distance of ten or more Debye lengths. In contrast to the quadripole probe, this ‘double-dipole probe’ relies on not producing perturbations in the plasma, rather than on minimizing their effects. The plasma is assumed to be warm and isotropic, and the motion of the ions is neglected. First, it is shown that, in a Maxwellian plasma, the frequency response of a double-dipole probe is easier to interpret than that of a quadripole probe with the customary square layout. Then, in a second step, the transfer impedance of the former probe is calculated in a Cauchy plasma, and the results are compared with those previously obtained in a Maxwellian plasma. By so doing, we show that, for large distances between the dipoles, the real part of the transfer impedance is sensitive to the form of the tail of the distribution function.
TL;DR: The variation of refractive index with concentration was measured at infrared wavelengths for 3 suspensions using a laser source and a modified version of the original Debye (1946) method.
Abstract: The variation of refractive index with concentration was measured at infrared wavelengths for 3 suspensions using a laser source and a modified version of the original Debye (1946) method.
TL;DR: The rotational transitions of 4-cyanopyridine, 3-cyaneopyridines and 2-cyclopyride have been observed and assigned in this article.
TL;DR: In this article, surface and edge vibrational modes were incorporated into the Debye spectrum and two additional terms, which depend on the surface/volume and edge-length/volume ratios, appeared therefore in the expression for the scattered intensity.
Abstract: The influences of sample size and mosaic block size upon X-ray thermal diffuse scattering have been investigated. Surface and edge vibrational modes were incorporated into the Debye spectrum. Two additional terms, which depend on the surface/volume and edge-length/volume ratios, appear therefore in the expression for the scattered intensity. The TDS contributions of the volume and surface terms to the integrated Bragg intensity are calculated numerically.
TL;DR: In this paper, a simple formula is derived which expresses the Debye temperature of a disordered multicomponent alloy with small atomic radius disparity in terms of the debye temperatures of the pure components, the mole fractions of the components, and a set of undetermined parameters, each of which can be found from the deboe temperature for one composition of each possible binary alloy made from the components.
Abstract: A simple formula is derived which expresses the Debye temperature of a disordered multicomponent alloy with small atomic radius disparity in terms of the Debye temperatures of the pure components, the mole fractions of the components, and a set of undetermined parameters, each of which can be found from the Debye temperature for one composition of each possible binary alloy made from the components. The formula is an improvement on a similar formula for the binary case due to Mitra and Chattopadhyay because the physical significance of the undetermined parameters is more readily apparent. The influence of short-range order in the binary case is considered. Application is made to the Ag-Au-Pd, Cr-Fe, and Cu-Ni systems in order to test the formula.
TL;DR: In this paper, the temperature dependence of the integrated intensity under the Bragg peak does not reveal any deviations from its normal behaviour, i.e., an essentially linear increase of the mean square vibrational amplitude of the lattice atoms as a function of temperature between 10 °C and a temperature at least 10−4 °C close to the melting temperature.
Abstract: Premelting phenomena have been searched for in pure, perfect gallium crystals by using anomalous X-ray transmission. The temperature dependence of the integrated intensity under the Bragg peak does not reveal any deviations from its normal behaviour, i.e. an essentially linear increase of the mean square vibrational amplitude of the lattice atoms as a function of temperature between 10 °C and a temperature at least 10−4 °C close to the melting temperatureT
m
=29.75 °C. The temperature dependence of the integrated intensity of the 020-reflection can be described by a Debye temperatureΘ
(020)=189±6 K. Premelting effects could not be detected.
TL;DR: In this paper, the temperature dependence of the Debye temperatures of nine face-centred and nine body-centered cubic elements have been calculated from previous elastic-constant measurements, and the results have been used to derive the anharmonic pair potential of each element by means of a nearest-neighbour central force theory.
Abstract: The temperature dependence of the Debye temperatures of nine face-centred and nine body-centred cubic elements have been calculated from previous elastic-constant measurements. The results have been used to derive the anharmonic pair potential of each element by means of a nearest-neighbour central force theory. A new criterion for melting is proposed, and its results for the above-mentioned materials are seen to be in excellent agreement with experimental values.
TL;DR: In this article, the basic results of the superconducting proximity effect have been generalized to apply to strong-coupling systems, and the theoretical results are compared with experimental data on thin films and eutectic alloys.
Abstract: Some of the basic results of the theory of the superconducting proximity effect have been generalized to apply to strong-coupling systems. The results agree with Moormann's theory of the proximity effect between weak-coupling superconductors with different Debye frequencies and also indicate that logarithmic frequency averaging is correct. The theoretical results are compared with experimental data on thin films and eutectic alloys, and the agreement is very good. (AIP)
TL;DR: In this paper, the variation of the Debye-Waller factors of silver, gold and lead with temperature can be described by means of the nearest neighbour central force pair interaction theory of Killean.
Abstract: It is shown that the variation of the Debye-Waller factors of silver, gold and lead with temperature can be described by means of the nearest neighbour central force pair interaction theory of Killean. Expressions for the temperature dependence of the Debye temperatures of six cubic elements are obtained from previous X-ray and neutron diffraction measurements, and the anharmonic pair potential has been derived in each case.
TL;DR: In this article, the authors derive a general method for obtaining the interaction energy of a system of charged bodies immersed in an electrolyte, based on a formalism due to R. A. Craig.
Abstract: Starting with a formalism due to R. A. Craig, we derive a general method for obtaining the interaction energy of a system of charged bodies immersed in an electrolyte. This formalism embodies terms which have previously been obtained from theories of the electrostatics and dispersion forces, unifying and extending previous methods. In the applications considered here, we have specialized to flat plates with small surface charges, obtaining many known results (due to Debye and Huckel, Onsager and Samaras, Verwey and Overbeek). In addition we find corrections to the pressure between overlapping double layers which can be significant compared to the classical expressions.