Showing papers on "Debye published in 1986"
TL;DR: Results of perturbative calculations in high-temperature Yang-Mills theory suggest the need for examining a gauge-invariant electrostatic correlation function that is free from color averaging, and show the emergence of the magnetostatic mass gap as the dominant decay mass of this correlation.
Abstract: The non-Abelian analogue of the Debye screening effect is investigated by means of perturbative calculations in high-temperature Yang-Mills theory. It is recalled that the gluon vacuum-polarization tensor, which is gauge dependent, does not directly yield the Debye screening mass beyond leading order. Instead, the correlation function of two Polyakov loops, representing the color-averaged potential energy of a static quark-antiquark pair, is examined as a possible means of defining a gauge-invariant Debye mass. Though apparently satisfactory to leading order, an examination of higher orders reveals two problems: (i) an unexpected breakdown of perturbation theory in the electrostatic sector and (ii) the emergence of the magnetostatic mass gap as the dominant decay mass of this correlation. These results might be the signal for a breakdown of gauge symmetry in the plasma phase and indicate the need for examining a gauge-invariant electrostatic correlation function that is free from color averaging.
138 citations
TL;DR: In this article, the authors simulate photon-induced electron transfer within specially synthesized molecular assemblies in which a donor moiety is separated from an electron acceptor by a rigid, saturated hydrocarbon framework of variable length, from 5 to 13 A.
Abstract: The primary steps in photosynthesis involve very rapid (sub-nanosecond) electron transfer between molecular entities that are rigidly embedded within a lipid membrane and separated from each other by well-defined distances on the order of 10 A. In an attempt to simulate such systems we have studied photon-induced electron transfer within specially synthesized molecular assemblies in which a donor moiety is separated from an electron acceptor by a rigid, saturated hydrocarbon framework of variable length, from 5 to 13 A. We find charge separation to occur on a sub-nanosecond timescale with close to unit quantum efficiency in all cases. The lifetimes of the resulting charge-transfer states, with dipole moments approaching 70 debye units, can extend to several hundred nanoseconds. Non-conjugated hydrocarbon bridges may be important in determining the rate and direction of electron transfer in photo-excited natural or artificial molecular systems.
116 citations
TL;DR: It is found that most perturbative results, even the supposedly well-established low-order ones, would be affected and take the study of the quark-gluon plasma well out of the reach of perturbation theory and make nonperturbative techniques indispensable even at very high temperatures.
Abstract: The problems encountered in an earlier attempt to compute the non-Abelian Debye screening mass are rectified by considering the correlation of the eigenvalues of the untraced Polyakov loop. This gauge-invariant function is free from color averaging and is shown to yield the singlet potential of a static quark-antiquark pair at finite temperature. A perturbative computation requires that the electrostatic potential A/sub 4/ be endowed with a gauge-symmetry-breaking vacuum expectation value, the occurrence of which would explain the breakdown of perturbation theory encountered in the earlier calculation. While the symmetry breakdown cannot reliably be seen perturbatively, its effects on perturbative calculations can be assessed. It is found that most perturbative results, even the supposedly well-established low-order ones, would be affected. This would take the study of the quark-gluon plasma well out of the reach of perturbation theory and make nonperturbative techniques indispensable even at very high temperatures.
98 citations
TL;DR: In this article, an effective Debye temperature of 165 K was derived from the thermal behavior of the extended x-ray absorption fine-structure Debye-Waller factors.
Abstract: The ${L}_{3}$ edge of bulk Au has been studied using x-ray-absorption spectroscopy in the temperature range 16--300 K. An effective Debye temperature of 165 K is derived from the thermal behavior of the extended x-ray absorption fine-structure Debye-Waller factors. Their behavior is also calculated for finite systems by using a free-bounded-sphere density of states and a Debye approximation for the phonon spectra. An excellent agreement is found with experimental data previously reported on Au clusters with mean diameters ranging from 15 to 43 A\r{}. This confirms that the dynamic properties of Au clusters are well described by a liquid-drop model in agreement with heat-capacity measurements.
61 citations
TL;DR: In this paper, a macroscopic theory of exponential repulsion between lipid membranes (hydration forces) is proposed based on non-local water electrostatics and generalizes the Gouy-Chapman theory of the electric double layer for the case of surfaces carrying dipoles.
50 citations
TL;DR: In this article, the rate of electron transfer in polar media is calculated in the framework of the transition state theory, and it is shown that this theory is valid if k B T > (hω 0/2π), where ω 0 is the frequency of a particle motion at the barrier top.
Abstract: The rate of electron transfer in polar media is calculated in the framework of the transition state theory. It is shown that this theory is valid if k B T > (hω0/2π), where ω0 is the frequency of a particle motion at the barrier top. The pre-exponential factor of the rate constant is found to be dependent on the reaction heat, dielectric loss spectrum, ϵ(ω), and the nondiagonal matrix element, Г. The rate constant of charge transfer in water, with allowance for the resonance absorbtion region, is determined. The influence of the motion of the water complexes on the rate constant is considered and it is shown that the pre-exponential factor depends not only on the frequency of the complex vibrations, but also on its reorganization energy. The maximum value of the complex reorganization energy is calculated under the conditions where the theory is valid. In the particular case of the Debye dielectric loss spectrum the multidimensional activated complex theory is shown to be equivalent to the stochastic Alex...
38 citations
35 citations
TL;DR: In this paper, a method to characterize the photorefractive parameters of Bi12GeO20 crystal is described, where an analysis of the transient photoinduced grating under an external applied electric field allows to determine both the diffusion length and the Debye's screening length which are the important parameters for device applications.
31 citations
TL;DR: In this article, a mixing between e and f Λ doublet states of cw laser excited NaK (B 1 Π, v = 5, J = 4−24) has been observed.
30 citations
TL;DR: In this paper, the authors discuss some Abelian lattice gauge models of the noncompact variety, including models of relativistic and nonrelativistic plasmas, and show absence of exponential clustering for some observables in some domains in parameter space.
Abstract: We discuss some Abelian lattice gauge models of the noncompact variety, including models of relativistic and nonrelativistic plasmas. For all these models we show absence of exponential clustering for some observables in some domains in parameter space. We comment on the physical meaning of these results, in particular with respect to Debye screening of static electric charges.
29 citations
TL;DR: In this article, the specific heat of various pure, crystalline ferroelectrics was measured between 0.5 K and 40 K. In contrast to earlier results the calculated Debye temperatures, θ 0D, are in excellent agreement with values deduced from elastic constants.
Abstract: The specific heat of various pure, crystalline ferroelectrics—LiNbO3, LiTaO3, NaNO2, BaTiO3, TGS—has been measured between 0.5 K and 40 K. For all samples we observe a pure Debye's T3-dependence of the heat capacity as expected for the low temperature limit (T < θ0D/50). No excess heat capacity could be detected. In contrast to earlier results the calculated Debye temperatures, θ0D, are in excellent agreement with values deduced from elastic constants. Possible origins of previously reported excess heat capacities in numerous ferroelectrics are discussed; it is strongly suggested that these excess heats result from the presence of statistically distributed dipolar defects.
TL;DR: In this paper, a dynamic bond percolation model is extended and applied to polymer electrolytes by assuming an approximate form for the relaxation of the carrier mean-square displacement to its asymptotic value below the threshold, with similar assumptions for the short-range motion of the ionic charges bound to the polymer host.
TL;DR: For the Co-P-O glass system, data have been assembled on acoustic Debye temperature obtained from ultrasonic wave-velocity measurements, acoustic and optical Debye temperatures determined from infrared absorption studies, and optical debye temperatures obtained from electrical conductivity measurements as discussed by the authors.
Abstract: For the Co-P-O glass system, data have been assembled on acoustic Debye temperatures obtained from ultrasonic wave-velocity measurements, acoustic and optical Debye temperatures determined from infrared absorption studies, and optical Debye temperatures obtained from electrical conductivity measurements. It is argued that these quantities are systematically related in theory, and the relationships are substantiated by the experimental data.
TL;DR: In this paper, the permanent dipole moment, α, and the electrical polarizability of the purple membrane were measured in dc and ac electric fields and three parameters were obtained: the permanent Dipole Moment (PM), α and the retinal angle.
01 Mar 1986-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this paper, it was shown that calculations incorporating accepted values of Debye temperatures for C (diamond), Si, Ge, and GaAs lead to excellent agreement with experiment for all cases, save Si.
Abstract: The energies of photons arising from transitions between low-lying bound states of channeled electrons are sensitive to the lattice vibration amplitude. It is shown that calculations incorporating accepted values of Debye temperatures for C (diamond), Si, Ge, and GaAs lead to excellent agreement with experiment for all cases, save Si. Channeling radiation data from Si are then used to derive a Debye temperature which is shown to be consistent with temperature dependent measurements in both planar and axial channeling.
TL;DR: A quantum theory of formation and propagation of superfluorescence and Stokes pulses in samples of small Fresnel numbers is presented and it is pointed out that due to guiding effects, if the Fresnel number is smaller than unity, the contribution from totally reflected rays is not negligible with respect to that from nonreflected rays.
Abstract: A quantum theory of formation and propagation of superfluorescence and Stokes pulses in samples of small Fresnel numbers is presented. Linearized Maxwell-Heisenberg equations for the system of two-level atoms and a quantized electromagnetic field are solved analytically in the second-order Debye approximation. Under this approximation paths of rays which undergo one reflection from the sides of the sample and those which propagate without reflections are studied. We point out that due to guiding effects, if the Fresnel number is smaller than unity, the contribution from totally reflected rays is not negligible with respect to that from nonreflected rays. This leads to the interference between reflected and nonreflected rays which affects spatial properties of superfluorescence and Stokes pulses. Moreover, as a consequence of guiding effects, the spectral density of light becomes asymmetric and shifted from the atomic resonance frequency.
TL;DR: The first triaheptafulvalenes (10, 13) were available by Peterson olefination of the corresponding cycloproparene as mentioned in this paper, and small hypsochromic shifts were noted in their uv spectra; the dipole moments of (8) and (12) are 2.6 and 1.2 Debye respectively.
TL;DR: In this article, a simple model was proposed to describe satisfactorily the measured data and the specific heat calculated from this density of states, in addition to the Debye term, is in good agreement with data in the literature.
Abstract: Inelastic neutron scattering from vitreous silica reveals that, in addition to the sound waves, there is a strong contribution from other vibrational modes in the frequency region above 150 GHz. From an analysis of their inelastic structure factor, we have put forward a simple model which can describe satisfactorily the measured data. The additional modes are identified as coupled rotations of SiO 4 tetrahedra and their density of states is determined on an absolute scale. The specific heat calculated from this density of states, in addition to the Debye term, is in good agreement with data in the literature. Some comments are made on the fracton interpretation of the vibrational density of states of amorphous solids.
TL;DR: The results show that floating monolayers of Ar and Xe represent their physisorbed counterparts well and show that Xe and Kr are effectively harmonic at T &25 K while Ne is a strongly anharmonic 2D crystal at all T.
Abstract: The dynamics of floating two-dimensional {2D) monolayers of Xe, Kr, Ar, and Ne are explored over a range of lattice spacings and temperature using the self-consistent phonon theory. Phonon dispersion curves and the zero-point energy are calculated and appropriate Debye temperatures and rms vibrational amplitudes (u2) estimated at T =0 K. The results show that floating monolayers of Ar and Xe represent their physisorbed counterparts well. They also show that Xe and Kr are effectively harmonic at T &25 K while Ne is a strongly anharmonic 2D crystal at all T. The selfconsistent harmonic frequencies in Ne at T =0 K are nearly twice the harmonic values. Ar is an intermediate case. The effective Debye temperature is ea -65 K in all cases and the Lindemann ratio y = (u ') /R varies from 3% in Xe to 9% in Ne at T =0 K, similar to 3D crystal values. The phonon frequencies depend sensitively on lattice parameter and temperature, more so than in 3D crystals.
Journal Article•
TL;DR: In this article, the mean square amplitudes of vibration and associated Debye temperatures of hexagonal Dy, Gd, Lu and Y have been obtained from X-ray intensities.
Abstract: The directional mean square amplitudes of vibration and associated Debye temperatures of hexagonal Dy, Gd, Lu and Y have been obtained from X-ray intensities. The integrated intensities have been measured with a Philips PW 1051 powder diffractometer fitted with a proportional counter using CuK sub z radiation at room temperature and have been corrected for thermal diffuse scattering. The experimental values of directional Debye temperature have been compared with corresponding values obtained from theoretical calculations. Values of energy of vacancy formation for the metals studied have been estimated using a relation connecting it with the Debye temperature given by H.R. Glyde (J. Phys. Chem. Solids , 1967, 28, 2061).
TL;DR: In this article, the precision lattice parameters and the coefficients of thermal expansion of KCl, KBr, and their solid solutions have been determined as a function of temperature by an X-ray method using a high-temperature powder camera.
Abstract: The precision lattice parameters and the coefficients of thermal expansion of KCl, KBr, and their solid solutions have been determined as a function of temperature by an X-ray method using a high-temperature powder camera. From the X-ray diffractograms obtained at room temperature the Debye-Waller factors, Debye temperatures and the root mean square amplitudes of vibration of these mixed crystals have been evaluated. A linear relationship is obtained between the lattice parameter and the composition of the solid solution in accordance with Vegard's law. Both of the thermal parameters, the thermal expansion coefficient and the root mean square amplitude of thermal vibration, vary non-linearly with increasing mole percentage of KBr, the deviation from linearity being maximum around equimolar concentration. The composition dependence of these parameters is discussed in relation to a number of physical properties of these mixed crystals available in the literature.
TL;DR: In this article, the theory of screening of Debye and Huckel is shown to be a combined classical and mean field limit of charge symmetric quantum Coulomb systems with Boltzmann statistics.
Abstract: In this paper, we consider charge symmetric quantum Coulomb systems with Boltzmann statistics. We prove that the theory of screening of Debye and Huckel is a combined classical and mean field limit of these quantum Coulomb systems.
TL;DR: In this article, the factors of iron carbonitride debye temperatures of 360 K and 620 K have been studied, where one and two interstitial nearest neighbors have been found.
Abstract: f-Factors of iron atoms, whith one and two interstitial nearest neghbours, in an iron carbonitride has been studied. Debye temperatures of 360 K and 620 K respectively, has been found.
TL;DR: In this paper, the specific heats of the semiconducting compounds ZrSe3 and ZrS3 have been measured in the temperature range between 8 and 200 K at the lowest values of T, yielding a characteristic Debye temperature at absolute zero θD(0) = 110 ± 2 K in satisfactory agreement with the value extracted from the available experimental sound velocities.
TL;DR: In this article, a theory for the dispersion and attenuation of sound waves due to amplitude and phase fluctuations of the order parameter in incommensurate solids is developed.
Abstract: A theory for the dispersion and attenuation of sound waves due to amplitude and phase fluctuations of the order parameter in incommensurate solids is developed. Using Langevin equations for acoustic and order parameter modes we obtain a Debye behavior for the elastic response at “high” frequencies and a strongly non-Debye behavior at “low” frequencies due to infrared divergences of simple perturbation theory. The divergences are treated by summing up the leading diagrams of a 1/N expansion where N is the number of components of the order parameter. At low frequencies the dispersion of sound waves is only little affected by the divergences; however their absorption increases dramatically in pure systems, leading to diverging viscosities throughout the incommensurate phase and an anomalous ω3/2 law for the ultrasonic attenuation coefficient. We discuss also how the anomalous elastic response at low frequencies changes if a finite coherence length due to pinning effects is taken into account. Finall...
TL;DR: In this paper, it was shown that the generalised conductivity of a suspension of components whose conductivities are represented by a sum of Debye type contributions can also be expressed as a superposition of debye terms.
Abstract: It is shown that, according to the Maxwell mixture formula, the generalised conductivity of a suspension of components whose conductivities are represented by a sum of Debye type contributions can also be expressed as a superposition of Debye terms. Their number is n+2 m+1, where n(m) is the number of Debye terms representing the particles (continuum) and the last addend appears when at least one of the components is conducting. The special case where n=m=1 is analysed in detail and the interpretation of data from ionic micelles in an electrolyte is discussed.
TL;DR: A central oscillator coupled to a bath of harmonic oscillators with a two-dimensional Debye spectrum is set up as a model for the dynamics of strongly coupled linear systems, where the bath oscillators are eliminated from the central oscillators' equation of motion, other than for initial conditions.
Abstract: A central oscillator coupled to a bath of harmonic oscillators with a two-dimensional Debye spectrum is set up as a model for the dynamics of strongly coupled linear systems. The bath oscillators are eliminated from the central oscillator's equation of motion, other than for initial conditions. The resulting Langevin equation is solved analytically for two different initial conditions for the bath. In one case, the bath oscillators are started at finite temperature and the coupling is turned on suddenly, and in the other they are adiabatically heated with constant coupling. The problem of equipartitioning of the kinetic energy, the velocity autocorrelation function of the central oscillator, and its spectral distribution are examined for various values of the physical parameters. The analytical results of the sudden case are compared with molecular-dynamics calculations and excellent agreement is found.
TL;DR: In this paper, the heat capacity at constant pressure, Cp, of single-phase, face-centered cubic ScDx (x=1.75, 1.83,1.91, and 1.99) was measured from room temperature to 950 K, and analyzed in terms of various contributions of the deuterium and metal constituents.
Abstract: The heat capacity at constant pressure, Cp, of single‐phase, face‐centered cubic ScDx (x=1.75, 1.83, 1.91, and 1.99) was measured from room temperature to 950 K, and analyzed in terms of various contributions of the deuterium and metal constituents. Values ranged from approximately 40 to 80 J mol−1 K−1 with increasing temperature. The heat capacity at constant volume was assumed to be composed of lattice contributions from an acoustic vibrational mode, Cl(a)v, and an optical vibrational mode, Cl(o)v, plus an electronic contribution, Cev. The acoustic part, Cl(a)v, was evaluated as a Debye term with characteristic Debye temperatures calculated from measured values of temperature‐dependent acoustic velocities and lattice constants. An isotope‐adjusted Einstein temperature, derived from inelastic neutron scattering measurements on ScH2, was used to find Cl(o)v. The Cev term was evaluated from a published value of the electronic heat capacity constant for ScH2 (assumed to be the same for ScD2). Particular att...
TL;DR: In this paper, the three independent elastic constants C11, C12, C44 of solid solutions of ionic compounds have been expressed in terms of those of the constituent compounds, their molecular fractions and lattice constants.
Abstract: The three independent elastic constants C11, C12, C44 of solid solutions of ionic compounds have been expressed in terms of those of the constituent ionic compounds, their molecular fractions and lattice constants. Three relationships which have been considered to obtain the expressions are: (i) the expression of Giri and Mitra (1985) for Debye temperatures of solid solutions in terms of those for constituent compounds; (ii) the expression of Shirley (1975) connecting force constants and Debye temperatures; and (iii) expressions of Niu and Shimizu (1967) connecting force constants with elastic constants. The values obtained for C11, C12 and C44 are in excellent agreement with the experimental values for NaCl-NaBr, KCl-KBr, KBr-KI and AgCl-AgBr systems.
TL;DR: In this article, a simplified analytical model for the ion generation rate is used to give an estimate of the breakdown threshold intensity, where the Debye criterion has been used in the sense of a plasma definition.
Abstract: Ionization by multiphoton processes is the dominant generation mechanism of first electrons in the UV-laser-induced gas breakdown A strongly simplified analytical model for the ion generation rate is used to give an estimate of the threshold intensity I th The result is compared to descriptions by Keldish [1] and Bebb [2] to check its limits of applicability Solving the kinetic conservation equations for the focus volume gives an estimation of the breakdown intensity where the Debye criterion has been used in the sense of a plasma definition As an example, breakdown experiments with a KrF-excimer laser have been carried out at different pressures in an argon atmosphere The pressure dependency of the breakdown threshold intensity and its order of magnitude are predicted by the model