Showing papers on "Debye published in 1993"
TL;DR: A crossover from a Debye-like to a non-Debye behavior at a characteristic time which is effectively independent of temperature and momentum transfer Q is observed.
Abstract: The dynamics of a very fragile glass-forming polymer is studied by time of flight neutron scattering in a time scale from 10 -13 to 10 -11 s. We observe a crossover from a Debye-like to a non-Debye behavior at a characteristic time which is effectively independent of temperature and momentum transfer Q. We also confirm the results previously obtained about the non-Debye a relaxation in a different time scale (10 -11 to 10 -8 s). The results here reported open a new outlook for understanding the fast dynamics of glass-forming systems
161 citations
TL;DR: In this paper, the asymptotic behavior of the ionic pair correlation functions is formally analyzed, and exact expressions for the decay length and the effective charge on the ions in terms of the direct correlation function are given for monovalent aqueous electrolytes.
Abstract: The multicomponent primitive model electrolyte is analyzed using the Ornstein-Zernike equation and the asymptotic behavior of the direct correlation function. An approximation for the screening length is derived from the second-moment condition, κ=κ D /√1-(κ D d) 2 /2+(κ D d) 3 /6 where κ D -1 is the Debye length and d is the ion diameter. This is accurate up to 1M concentration for monovalent aqueous electrolytes and considerably extends the range of validity of the classical Debye- Huckel theory. The asymptotic behavior of the ionic pair correlation functions is formally analyzed, and exact expressions are given for the decay length and the effective charge on the ions in terms of the direct correlation function
135 citations
TL;DR: In this article, the lifetime of P870*, the primary electron-donor state, is invariant to location of [omega][sub B] within the inhomogeneous distribution of the P870 zero-phonon line transition frequencies for both the protonated and deuterated reaction center of the purple bacterium Rhodobacter sphaeroides.
Abstract: Photochemical hole-burned spectra with improved signal-to-noise ratio ([times]20) are reported for the protonated and deuterated reaction center of the purple bacterium Rhodobacter sphaeroides Spectra obtained as a function of burn frequency ([omega][sub B]) establish that the lifetime of P870*, the primary electron-donor state, is invariant to location of [omega][sub B] within the inhomogeneous distribution of P870 zero-phonon line transition frequencies For both the protonated and deuterated RC, which exhibit P870 absorption widths at 42 K of only 440 and 420 cm[sup [minus]1], the zero-phonon holes yield a lifetime of 093 [+-] 010 ps This lifetime is independent of temperature between 16 and 80 K (range over which the zero-phonon hole could be studied) The invariance of the P870* lifetime to [omega][sub B] and other data indicates that the nonexponential decay of P870* (Vos et al Proc Natl Acad Sci USA 1991, 88, 8885) is due neither to a distribution of values from the electronic coupling matrix element associated with electron transfer, which one might expect from the normal glasslike structural heterogeneity of the RC, nor to gross heterogeneity The higher quality of the hole spectra has allowed for more stringent testing of the theoretical model previously used to simulate themore » P870 hole profiles and absorption spectrum Although the essential findings reported earlier (see, eg, Reddy et al Photosyn Res 1992, 31, 167) are not altered, it is concluded that the modeling of the distribution of low-frequency phonons (mean frequency approximately 30 cm[sup [minus]1]), which couples to P870*, in terms of a Debye distribution is inadequate The anomalous low-frequency modes of glasses and polymers are suggested to be important also for proteins 60 refs, 8 figs, 2 tabs« less
100 citations
TL;DR: It is shown that, after a resummation of leading high-temperature contributions, a complete and gauge-independent result for the non-Abelian Debye screening mass at next-to-leading order can be extracted from the static gluon propagator.
Abstract: It is shown that, after a resummation of leading high-temperature contributions, a complete and gauge-independent result for the non-Abelian Debye screening mass at next-to-leading order can be extracted from the static gluon propagator. In contrast with previous, incomplete results, the correction to the Debye mass is found to be logarithmically sensitive to the nonperturbative magnetic mass and positive, in accordance with recent high-statistics results from lattice calculations.
99 citations
TL;DR: In this article, the recursive convolution method is extended to three-dimensional scattered field calculations and the accuracy of the method is demonstrated by calculating scattering from spheres of various sizes composed of three different types of frequency-dependent materials.
Abstract: An efficient method to include frequency-dependent materials in finite difference time domain calculations based on the recursive evaluation of the convolution of the electric field and the susceptibility function has previously been presented. The method has been applied to various materials, including those with the Debye, Drude, and Lorentz forms of complex permittivity, and to anisotropic magnetized plasmas. Previous demonstrations of this approach have been confined to total field calculations in one dimension. In this paper the recursive convolution method is extended to three-dimensional scattered field calculations. The accuracy of the method is demonstrated by calculating scattering from spheres of various sizes composed of three different types of frequency-dependent materials. >
88 citations
TL;DR: In this article, a new mathematical representation of the cluster model for dielectric relaxation, in a bound dipole case, was established by employing the extremal value theory, and two distinct probabilistic mechanisms, which drive the response function to acquire the power-law form, were presented.
Abstract: A new mathematical representation of the cluster model for dielectric relaxation, in a bound dipole case, is established by employing the extremal value theory. Two distinct probabilistic mechanisms, which drive the dielectric response function to acquire the power-law form, are presented. Consequently, two forms of self-similarity, one of which dominates the response at short times and the other at long times, leading to a general relaxation equation, are identified. Finally, the conditions under which the derived response function takes the well known empirical forms (Williams-Watts, Cole-Cole, Cole-Davidson, 'broadened' Debye, and 'flat loss' responses) are recognized.
82 citations
01 Feb 1993
TL;DR: In this article, an analysis of the effects of polarization of the double layer on the diffusiophoretic mobility of spherical, uniformly charged colloidal particles is presented, based on the concepts first proposed by S. Dukhin and B. V. Derjaguin (in "Surface and Colloid Science" (E.S. Matijevic, Ed.), Vol. 7.
Abstract: An analysis of the effects of polarization of the double layer on the diffusiophoretic mobility of spherical, uniformly charged colloidal particles is presented. The development is based on the concepts first proposed by S.S. Dukhin and B. V. Derjaguin (in "Surface and Colloid Science" (E. Matijevic, Ed.), Vol. 7. Wiley, New York, 1974). The double layer is assumed very thin relative to the radius (R) of the particle, κR ⪢ 1, where κ is the Debye screening parameter, but the dimensionless zeta potential (ζ) is allowed to be arbitrarily large such that the parameter λ = (κR) -1 [exp(ζ/2) - 1] could be O (1). The theory is linear in the macroscopic gradient of electrolyte concentration and hence the mobility depends only on ζ and λ. An analytical expression for this dependence is derived for the case of a symmetrically charged electrolyte. This equation is compared with results based on numerical solutions of the governing electrokinetic equations; the agreement is excellent for κ R > 20, and our analytical expression even captures the change in direction of the particle motion as λ increases, which is predicted by the numerical results. The polarization model is extended to general electrolytes in order to demonstrate effects of differences in the valences of the two ions.
69 citations
TL;DR: In this article, a dephasing dynamical contribution in an intermediate time scale is needed in addition to a slower Debye reorientation relaxation and a faster broad inhomogeneous oscillator.
Abstract: Depolarized Rayleigh‐wing spectra of simple liquids, including CS2, chlorinated methanes, benzene and benzene derivatives have been recorded using stimulated gain spectroscopy. To adequately interpret these spectra of simple liquids, a dephasing dynamical contribution in an intermediate time scale is needed in addition to a slower Debye reorientation relaxation and a faster broad inhomogeneous oscillator. The curve‐fit dynamical characteristic parameters of these simple liquids are tabulated for comparison. The microscopic molecular properties, shape anisotropy, and dominating moment of inertia are found to play an important role in determining the rates of interaction‐induced dynamics; smaller shape anisotropy and smaller moment of inertia give rise to faster collision rate in the intermediate frequency regime and faster oscillation in the higher frequency regime, respectively. In the low frequency region, the shear viscosity (a macroscopic property) of the liquid and the general molecular shapes dictate reorientation diffusion; for molecules within a family, the Debye relaxation rate is faster for liquids with smaller viscosity and shape anisotropy. Halogenation of benzene breaks the symmetry of the benzene ring giving two distinct oscillator frequencies. In the case of iodobenzene, three principle molecular axes are clearly distinct; it is necessary to use two Debye relaxation rates and two broad inhomogeneous oscillators to fit its stimulated gain spectrum.
62 citations
TL;DR: In this article, temperature dependence of EXAFS, EELFS and ARXPS is discussed in the framework of plane wave approximation, where they take the cubic and quartic anharmonicity into account.
Abstract: Temperature dependence of EXAFS, EELFS and ARXPS is discussed in the framework of plane wave approximation, where we take the cubic and quartic anharmonicity into account. First we apply cumulant expansion whose expanded terms are written in terms of corresponding lower order moments and cumulants. Secondly we apply temperature Green's function technique systematically to calculate these moments for perfect crystals with translational symmetry. We furthermore discuss high and low temperature behavior of these cumulants, and also describe real space representation of them in comparison with widely used classical expression. This real space representation needs no translation symmetry, and we discuss the applicability of the classical local space integral formula.
58 citations
TL;DR: The generating functional for hard thermal loops in quantum chromodynamics is important in setting up a resummed thermal perturbation theory, so that all terms of a given order in the coupling constant can be consistently taken into account.
Abstract: The generating functional for hard thermal loops in quantum chromodynamics is important in setting up a resummed thermal perturbation theory, so that all terms of a given order in the coupling constant can be consistently taken into account. It is also the functional which leads to a gauge-invariant description of Debye screening and plasma waves in the quark-gluon plasma. We have recently shown that this functional is closely related to the eikonal for a Chern-Simons gauge theory. In this paper, this relationship is explored and explained in more detail along with some generalizations.
49 citations
TL;DR: In this paper, the authors consider parabolic equations with nonlocal coefficients obtained from the Vlasov-Fokker-Planck equations with potentials and study the local in time existence of solutions to these equations with no-flux boundary conditions.
Abstract: We consider parabolic equations with nonlocal coefficients obtained from the Vlasov–Fokker–Planck equations with potentials. This class of equations includes the classical Debye system from electrochemistry as well as an evolution model of self-attracting clusters under friction and fluctuations. The local in time existence of solutions to these equations (with no-flux boundary conditions) and properties of stationary solutions are studied.
TL;DR: In this paper, an efficient technique for computing axisymmetric non-neutral plasma equilibria is described, which may be obtained either by requiring global thermal equilibrium, by specifying the midplane radial density profile, or by specifying a radial profile of ∫n dz.
Abstract: Efficient techniques for computing axisymmetric non‐neutral plasma equilibria are described These equilibria may be obtained either by requiring global thermal equilibrium, by specifying the midplane radial density profile, or by specifying the radial profile of ∫n dz Both splines and finite‐differences are used, and the accuracy of the two is compared by using a new characterization of the thermal equilibrium density profile which gives a simple formula for estimating the radial and axial gradient scale lengths of thermal equilibria It is found that for global thermal equilibrium 1% accuracy is achieved with splines if the distance between neighboring splines is about two Debye lengths while finite differences require a grid spacing of about one‐half Debye length to achieve the same accuracy
TL;DR: The dynamics of glass-forming liquids shows universal features like non-Debye behavior, scaling, and non-Arrhenius temperature dependence of the characteristic rates, but whether or not these features extend to the glass phase through the experimental liquid-glass transition is still unknown.
Abstract: The dynamics of glass-forming liquids shows universal features like non-Debye behavior, scaling, and non-Arrhenius temperature dependence of the characteristic rates. These features have been mainly established in the time range between 10 -9 and 10 s. It is well known that when the temperature of a glass-forming liquid is lowered and the characteristic relaxation time becomes larger than hundreds of seconds, the system falls out of equilibrium and a glass is obtained. However, whether or not the typical features of the glass-forming-liquid dynamics extend to the glass phase through the experimental liquid-glass transition, T g is still unknown
TL;DR: In this article, the authors considered four flavour QCD in the high-temperature phase and applied the well-established method of dimensional reduction to study the quark potential both at short distances, where perturbation theory is valid, as well as at large distances where screening sets in.
TL;DR: In this article, the problem of diffraction of a plane polarized wave by perfectly conducting cones of arbitrary cross sections is considered using the Debye scalar potentials and the Sommerfeld transformation.
Abstract: The problem of diffraction of a plane polarized wave by perfectly conducting cones of arbitrary cross sections is considered Using the Debye scalar potentials and the Sommerfeld transformation, th
TL;DR: In this article, the widths, positions and shapes of sharp luminescence lines of the Nd3+ ion in GSGG:Cr3+, Nd 3+ were measured carefully from 78 to 600 K. The Debye temperature of GSGG is estimated to be 500 K through the fitting of the theoretical formulas to the experimental data.
TL;DR: In this paper, it was shown that for dielectric Cole-Cole plots, e″ versus e′ as a function of frequency, there are two physical constraints: slope limiting ± ∞ and slope −0.
TL;DR: In this article, nonlinear dielectric relaxation spectra of two kinds of ferroelectric liquid crystals (FLC) are investigated in the chiral smectic C (SmC*) phase.
Abstract: Nonlinear dielectric relaxation spectra of two kinds of ferroelectric liquid crystals (FLC) are investigated in the chiral smectic C (SmC*) phase. The linear spectrum shows the relaxation of Debye type and the third-order nonlinear spectrum also shows the relaxation of Debye type generalized to the nonlinear case. The third-order nonlinear dielectric increment is found to be negative, which indicates that the dielectric nonlinearity of FLCs in the SmC* phase mainly originates from the saturation of molecular dipole moments induced by the applied electric field. The profiles of linear and nonlinear spectra remain almost unchanged throughout the SmC* phase. In the vicinity of the SmA-SmC* phase transition temperature, the linear spectrum shows the critical behavior of Curie-Weiss type and the third-order spectrum shows a sharp peak.
TL;DR: The Debye shielding is derived in a simple way without assuming Boltzmann's equilibrium as discussed by the authors, and conditions under which it applies and some of its consequences are discussed at the elementary level.
Abstract: The Debye shielding is derived in a simple way without assuming Boltzmann’s equilibrium. The conditions under which it applies and some of its consequences are discussed at the elementary level.
TL;DR: In this article, a simple and tractable modification to Debye's model is proposed which is free from the above-mentioned fault and the resulting Cole-Cole diagram is shown to deviate from an exact circle.
Abstract: Although Debye's relaxation model has been extensively used in analyzing experimental data of dielectric dispersion and absorption, the model has a fault to violate the sum rule for dielectric function. A simple and tractable modification to Debye's model is proposed which is free from the above-mentioned fault. The resulting Cole-Cole diagram is shown to deviate from an exact circle.
TL;DR: In this article, the survival probabilities in the Sumi-Marcus model of reversible electron transfer (ET) reactions, in which ligand vibrations and fluctuations in solvent polarization play important roles, are obtained numerically using a simple computer program suitable for use on a PC.
Abstract: The solution to an integral equation [J. Zhu and J. C. Rasaiah, J. Chem. Phys. 96, 1435 (1992)] for the survival probabilities in the Sumi–Marcus model of reversible electron‐transfer (ET) reactions, in which ligand vibrations and fluctuations in the solvent polarization play important roles, is obtained numerically using a simple computer program suitable for use on a PC. The solutions depend on the time correlation function Δ(t) of the reacting intermediates along the reaction coordinate which is shown to be equal to the time correlation function of the Born free energy of solvation of these intermediates even in discrete molecular solvents provided its response is linear. This enables Δ(t) to be determined accurately from time‐delayed fluorescence Stokes shift experiments or from dynamical theories of ion solvation; it is usually an exponential (Debye solvent) function of time or a sum of such exponentials (non‐Debye solvent). The solutions to the integral equation, which can be obtained numerically fo...
TL;DR: In this article, a simple model for the reproduction of the experimental heat capacities of urea, based on the Debye and Einstein functions, is described, and the debye characteristic temperature determined in this way was compared with those calculated from properties other than the heat capacity.
Abstract: The heat capacity of urea was measured with an adiabatic calorimeter in the temperature range 15–310 K. The data were extrapolated to 0 K by a model function to derive some standard thermodynamic functions including the enthalpy increments Δ 0 T H, the entropy increments Δ 0 T S, and the Giauque function (=Δ 0 TS −Δ 0 T H/T). A simple model for the reproduction of the experimental heat capacities of urea, based on the Debye and Einstein functions, is described. The Debye characteristic temperature determined in this way was compared with those calculated from properties other than the heat capacity. Any positive evidence of a suggested phase transition in urea around 190 K was not observed in the present heat capacity measurements. Possible existence of a phase with a Gibbs energy lower than that realized in the present investigation is discussed briefly.
TL;DR: The motion of a quantum particle in a random magnetic flux in two dimensions is investigated and a geometrical interpretation of effective single-particle action in these phases of Debye and Meissner phases is emphasized.
Abstract: The motion of a quantum particle in a random magnetic flux in two dimensions is investigated. Two situations are distinguished, a ``Debye'' phase where the fluxes are uncorrelated, and a ``Meissner'' phase where the fluxes appear as neutral pairs. A geometrical interpretation of effective single-particle action in these phases is emphasized. Results are discussed for (a) a continuum white-noise model where we employ a trial-action method, (b) a continuum model with randomly distributed flux tubes where we obtain the form of the Lifschitz tail, and (c) a lattice model, where numerical results for the density of states and diamagnetic response of Debye and Meissner phases are given. An important conclusion is that the density of states in the Debye phase exhibits a sharp peak at an effective band edge.
TL;DR: In this article, a non-linear dielectric relaxation spectroscopy was applied to soft materials such as polymers in the S*C phase of some ferroelectric liquid crystals.
Abstract: The non-linear dielectric relaxation spectroscopy has been recently developed and applied to soft materials such as polymers. We have applied this new method to the S*C phases of some ferroelectric liquid crystals. Under a weak AC electric field, the original and third order harmonic frequency components of electric displacement are proportional to the first and third powers of the applied electric field, respectively. The linear spectrum obtained from the original frequency component shows the relaxation of Debye type and the third order non-linear spectrum shows the relaxation with an extended form of Debye type to the non-linear case. The third order non-linear dielectric increment is found to be negative, which implies that the dielectric non-linearity of the liquid crystal in the S*C phase is due to the saturation of molecular dipole moments induced by the applied electric field. The temperature dependence of the linear and third order non-linear spectra in the S*C phase are also studied. Bo...
TL;DR: In this article, the authors used a linear approximation of the collision integral with respect to the electric field to obtain an additional term to the electrical conductivity of the plasma, which can be considered as an analogue to the well-known Debye-Onsager relaxation effect of electrolyte theory.
TL;DR: In this article, the phenomenon of Debye shielding in a dusty plasma consisting of Boltzmann electrons and ions, and negatively charged, massive dust grains is investigated, both small and large amplitude electrostatic potentials are considered and a parameter study conducted.
Abstract: The phenomenon of Debye shielding is investigated in a dusty plasma consisting of Boltzmann electrons and ions, and negatively charged, massive dust grains. Both small and large amplitude electrostatic potentials are considered and a parameter study conducted.
18 Aug 1993
TL;DR: In this paper, the dielectric properties of ice Ih (hexagonal ice) were measured at HF, VHF and microwave frequencies using several methods appropriate for each frequency range.
Abstract: The dielectric properties of ice Ih (hexagonal ice) were measured at HF, VHF and microwave frequencies using several methods appropriate for each frequency range. C-axis orientation dependence of the complex permittivity was particularly investigated because the dielectric anisotropy of the media determines the polarization state of the electromagnetic waves propagating in it and because it can cause the radio-echo internal reflections in the polar ice sheets. It was confirmed that the difference between the real part of the permittivity parallel to the c-axis and perpendicular to the c-axis is almost the same at HF and at microwave frequency. In addition, it was confirmed that the anisotropy of the loss tangent was about 20% at -22/spl deg/C at HF, i.e. at frequencies characterized by the high frequency tail of the Debye relaxation spectrum. This value is well explained mainly by the anisotropy in the dispersion strength and partly by the anisotropy in the relaxation time of Debye dispersion. In addition, these facts suggests this ratio hold over frequencies up to microwave where the absorption of the lattice vibration becomes dominant. >
TL;DR: In this paper, the mean Debye-WaUer factor (B)), Debye temperatures (OM) and long-range-order parameters (S) were evaluated for Ni3A1 alloys with various amounts of boron, hafnium, zirconium and titanium.
Abstract: Integrated intensities of Bragg reflections have been measured at room temperature for Ni3A1 alloys containing various amounts of boron, hafnium, zirconium and titanium and the data have been used to evaluate the mean Debye-Waller factors ((B)), Debye temperatures (OM) and long-range-order parameters (S). The Debye temperatures are observed to show a slight decrease with the decrease of aluminium content within the Ni3A1 phase. The results for the DebyeWaller factors indicate that additions of the ternary elements hafnium, zirconium and titanium cause the mean Debye-WaUer factor to increase linearly, while boron addition results in a nonlinear increase. The long-range-order parameter of stoichiometric Ni3A1 is 0.97, which decreases with decreasing aluminium concentration from the stoichiometric composition. The long-range-order parameter of Ni3A1 increases until 0.75 at.% B has been added, beyond that it remains constant. The long-range-order parameter of Ni3A1 increases initially with the addition of hafnium, zirconium and titanium up to 0.50at.% Hf and 0.52 at.%Zr, with further addition of hafnium and zirconium, it decreases. The results are discussed in relation to the crystal structure and chemical bonding in Ni3AI.
TL;DR: A theoretical formulation of coherent optical tunneling and the subsequent exchange of electromagnetic energy between two Mie-sized microspheres is presented and a useful analytical expression for the self- and mutual-coupling coefficients that are involved in the time-evolved coupled-mode equations is derived under a weakly coupling approximation.
Abstract: A theoretical formulation of coherent optical tunneling and the subsequent exchange of electromagnetic energy between two Mie-sized microspheres is presented. The coupled-mode theory of Debye potentials is used. A useful analytical expression for the self- and mutual-coupling coefficients that are involved in the time-evolved coupled-mode equations is derived under a weakly coupling approximation. Sample numerical results are shown for coupling between identical spheres.
TL;DR: In this article, the conditional electric potential around the ions is found by Poisson integration of the conditional charge densities calculated from the radial distribution functions found by the high precision canonical ensemble Monte Carlo simulations of some Z:Z, 2:1 and 1:1:1 primitive model electrolyte systems described in earlier studies.
Abstract: The conditional electric potential around the ions are found by Poisson integration of the conditional charge densities calculated from the radial distribution functions found by the high precision canonical ensemble Monte Carlo simulations of some Z:Z,2:1 and 1:1:1 primitive model electrolyte systems described in earlier studies. In most cases, the correspondance with the solution given by solving the linear Poisson-Boltzmann equation is very nearly perfect – at least not too far from contact. This is so in spite of the fact, that the linearisation condition of Debye and Huckel is violated near to contact in dilute solutions and in spite of the anticipation that the Debye-Huckel approximation should be of little relevance in more concentrated systems, where the Debye length is of the same order of magnitude as the ionic diameters. The linear Poisson-Boltzmann equation even continues to be of relevance in zones around ions of different sizes, where only part of the ions appearing in the solution ...