Showing papers on "Debye published in 2001"
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TL;DR: In this paper, Wang et al. applied the self-consistent hybrid approach to the spin-boson problem with Debye spectral density as a model for electron-transfer reactions in a solvent exhibiting Debye dielectric relaxation.
Abstract: The self-consistent hybrid approach [H. Wang, M. Thoss, and W. H. Miller, J. Chem. Phys. 115, 2979 (2001), preceding paper] is applied to the spin-boson problem with Debye spectral density as a model for electron-transfer reactions in a solvent exhibiting Debye dielectric relaxation. The population dynamics of the donor and acceptor states in this system is studied for a broad range of parameters, including the adiabatic (slow bath), nonadiabatic (fast bath), as well as the intermediate regime. Based on illustrative examples we discuss the transition from damped coherent dynamics to purely incoherent decay. Using the numerically exact results of the self-consistent hybrid approach as a benchmark, several approximate theories that have been widely used to describe the dynamics in the spin-boson model are tested: the noninteracting blip approximation, the Bloch–Redfield theory, the Smoluchowski-equation treatment of the reaction coordinate (Zusman equations), and the classical path approach (Ehrenfest model). The parameter range where the different methods are applicable are discussed in some detail.
260 citations
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TL;DR: In this article, numerical calculations on the field distribution in the focus of an optical system with high numerical aperture are presented, where diffraction integrals based on the Debye approximation are derived and evaluated for a radially polarized input field with a doughnut-shaped intensity distribution.
Abstract: We present numerical calculations on the field distribution in the focus of an optical system with high numerical aperture. The diffraction integrals which are based on the Debye approximation are derived and evaluated for a radially polarized input field with a doughnut-shaped intensity distribution. It is shown that this mode focusses down to a spot size significantly smaller as compared to the case of linear polarization. An experimental setup to measure the three-dimensional intensity distribution in the focal region is presented, which is based on the knife-edge method and on tomographic reconstruction.
228 citations
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TL;DR: In this article, the temperature dependence of the thermodynamic and dynamical properties of liquid water using the polarizable fluctuating charge (FQ) model is presented, both for a perfect lattice with no thermal disorder and at a temperature of 273 K, in contrast to nonpolarizable models, the FQ model has a density maximum of water near 277 K.
Abstract: The temperature dependence of the thermodynamic and dynamical properties of liquid water using the polarizable fluctuating charge (FQ) model is presented. The properties of ice Ih, both for a perfect lattice with no thermal disorder and at a temperature of 273 K, are also presented. In contrast to nonpolarizable models, the FQ model has a density maximum of water near 277 K. For ice, the model has a dipole moment of the perfect lattice of 3.05 Debye, in good agreement with a recent induction model calculation. The simulations at 273 K and the correct density find that thermal motion decreases the average dipole moment to 2.96 D. The liquid state dipole moment is less than the ice value and decreases with temperature.
186 citations
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TL;DR: In this article, the Debye temperature of a cubic element was calculated from the knowledge of all the elastic constants of the system, and the calculated results agree very well with the experimental data, and some empirical relationships have been observed between the high temperature entropy −Debye temperature θD(0) and the low temperature limit of the debye temperature −3.
128 citations
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TL;DR: The concept of thermal conductivity was introduced by Eucken and Debye as discussed by the authors, who showed that diamond was a reasonably good conductor for heat at room temperature and established theoretical support for this discovery.
Abstract: Every university student becomes familiar with the concept of thermal conductivity, a fundamental physical property of materials, through his or her textbooks. Initial work on high thermal conductivity was carried out in 1911 by Eucken, who discovered that diamond was a reasonably good conductor for heat at room temperature. Theoretical support for this discovery was established by Debye in 1914.
93 citations
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TL;DR: In this paper, the authors examined the nonlinear propagation of electron-acoustic waves in an unmagnetized, four-component plasma consisting of hot Maxwellian electrons, fluid cold and beam electrons and ions.
78 citations
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TL;DR: In this article, a simple model that treats the La ions as independent harmonic (Einstein) oscillators embedded in a Debye framework of boron ions successfully accounts for the anomalies in the specific heat and resistivity of hexaborides.
Abstract: ${\mathrm{LaB}}_{6}$ and other hexaborides are inclusion compounds in which the rare earth or other metal ion is weakly bound and sits in an oversized ``cage'' of boron ions Here we show that a simple model that treats the La ions as independent harmonic (Einstein) oscillators embedded in a Debye framework of boron ions successfully accounts for the anomalies in the specific heat and resistivity of ${\mathrm{LaB}}_{6}$ One of the nice features of the model is that the Einstein temperature of the La atoms and the Debye temperature of the boron framework are derived from room-temperature x-ray crystallography data This feature makes the model easy to apply to other hexaborides and other materials that can be treated as inclusion compounds The results from this work imply that local modes are likely to be important for understanding the physical properties of all the hexaborides
70 citations
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TL;DR: In this article, a model of the electron current in a plane plasma slab bounded by parallel dielectric walls in the presence of a homogeneous magnetic field perpendicular to the walls and an electric field oriented along the walls is presented.
Abstract: A model describing the phenomenon of the electron current in a plane plasma slab bounded by parallel dielectric walls in the presence of a homogeneous magnetic field perpendicular to the walls and an electric field oriented along the walls is presented. The current flows along the electric field because of the electron collisions with diffusely scattering walls. The model takes into account the presence of Debye layers and the non-Maxwellian character of the electron distribution function. Collisions in the plasma volume are ignored.
65 citations
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TL;DR: In this article, the authors use the technique of terahertz time-domain spectroscopy to experimentally and theoretically study the absorption and the dispersion of ammonia vapor.
Abstract: We use the technique of terahertz time-domain spectroscopy to experimentally and theoretically study the absorption and the dispersion of ammonia vapor. Our measurements show small deviations from the rotationinversion spectrum which originate from transitions in the O2 hot band and from the (NH3)2 dimer. We investigate the molecular tunneling in ammonia and apply our new molecular response theory to analyze the inversion spectrum of this molecule. The theory includes the molecular response of polar molecules to an external electric field over the duration of a collision with the molecular response time as a control parameter, and it unifies the basic collision theories of Lorentz, van Vleck -Weisskopf, and Debye. The calculated absorption and dispersion based on this theory fits the measurements over the full spectral range of the THz spectrum and allows to determine a response time of the order of 100 fs.
61 citations
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TL;DR: In this paper, general formulas for computing the radiation force exerted on arbitrarily oriented and arbitrarily shaped nonspherical particles due to scattering, absorption, and emission of electromagnetic radiation are derived, and for randomly oriented particles with a plane of symmetry, the formula for the average radiation force caused by the particle response to external illumination reduces to the standard Debye formula derived from the Lorenz-Mie theory.
Abstract: General formulas for computing the radiation force exerted on arbitrarily oriented and arbitrarily shaped nonspherical particles due to scattering, absorption, and emission of electromagnetic radiation are derived. For randomly oriented particles with a plane of symmetry, the formula for the average radiation force caused by the particle response to external illumination reduces to the standard Debye formula derived from the Lorenz-Mie theory, whereas the average radiation force caused by emission vanishes.
61 citations
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TL;DR: In this paper, the frequency-dependent complex dielectric permittivity of aqueous solutions of the homologous saccharides D(+)-glucose, maltose, and maltotriose in the frequency range 200 MHz to 20 GHz was investigated.
Abstract: We report the frequency-dependent complex dielectric permittivity of aqueous solutions of the homologous saccharides D(+)-glucose, maltose, and maltotriose in the frequency range 200 MHz⩽ν⩽20 GHz. For each solute, solutions having concentrations between 0.01 and 1 mol dm−3 were studied. In all measured spectra two dispersion/loss regions could be discerned. With the exception of the two most concentrated maltotriose solutions, a good description of the spectra by the superposition of two Debye processes was possible. The amplitudes and correlation times of the glucose and maltose solutions determined from fits of the experimental data were compared to those obtained in an earlier molecular dynamics study of such systems; the overall agreement between experiment and simulation is quite satisfactory. A dielectric component analysis of the simulation results permitted a more detailed assignment of the relaxation processes occurring on the molecular level. The physical picture emerging from this analysis is compared with traditional hydration models used in the interpretation of measured dielectric data. It is shown that the usual standard models do not capture an important contribution arising from cross terms due to dipolar interactions between solute and water, as well as between hydration water and bulk water. This finding suggests that conventional approaches to determine molecular dipole moments of the solutes may be problematic. This is certainly the case for solutes with small molecular dipole moments, but strong solute–solvent interactions, such as the saccharides studied here.
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TL;DR: In this paper, Tsytovich and de Angelis analyzed the collective shadow effect in dust charging and operate at distances larger than the previously known noncollective shadow attraction forces, and the dependence of the collective attraction forces on dust temperature was analyzed.
Abstract: The dust–dust collision integrals found in the kinetic theory of dusty plasmas [Tsytovich and de Angelis, Phys. Plasmas 6, 1093 (1999); 7, 554 (2000)] are analyzed. Analytic expressions are derived and numerical results are given for the case of thermal distributions to assess their importance and dependence on dusty plasma parameters. Modifications of Debye screening by collective dust effects are obtained. A study of the forces between two test dust particles is presented and the appearance of weakly screened attraction forces at distances larger than the Debye screening length is analyzed. These forces are related to the collective shadow effect in dust charging and operate at distances larger than the previously known noncollective shadow attraction forces. The dependence of the collective attraction forces on dust temperature is analyzed.
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TL;DR: In this article, the authors examined the equilibrium properties of hot, non-relativistic plasmas and obtained explicit results for density-density correlation functions through two-loop order and thermodynamic quantities through threeloop order.
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TL;DR: In this paper, the time evolution of the plasma distribution functions (electrons and ions) in dusty plasmas is found solving numerically the equations of the kinetic theory of dusty plaasmas.
Abstract: The time evolution of the plasma distribution functions (electrons and ions) in dusty plasmas is found solving numerically the equations of the kinetic theory of dusty plasmas [Tsytovich and de Angelis, Phys. Plasmas 6, 1093 (1999); 7, 554 (2000)]. The role and importance of the plasma source and particle diffusion are investigated. The “equilibrium” distributions (asymptotic solutions) are used to calculate the static screening of a dust particle, and the difference with the usual result (Debye screening) of a three-component plasma is shown for various parameter regimes.
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TL;DR: In this paper, the role of Coulomb and surface effects on the phase transition from dense nuclear matter to a mixed phase of nuclear and kaon-condensed matter was studied.
Abstract: We study the role of Coulomb and surface effects on the phase transition from dense nuclear matter to a mixed phase of nuclear and kaon-condensed matter. We calculate corrections to the bulk calculation of the equation of state (EOS) and the critical density for the transition by solving explicitly for spherical, cylindrical, and planar structures. The importance of Debye screening in the determination of the charged particle profiles is studied in some detail. We find that the surface and Coulomb contributions to the energy density are small, but that they play an important role in the determination of the critical pressure for the transition, as well as affecting the size and geometry of favored structures. This changes the EOS over a wide range of pressure and consequently increases the maximum mass by about 0.1 solar masses. Implications for transport properties of the mixed phase are also discussed.
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TL;DR: In this article, two molecular models of charged points and skewed rods were used to approximate inter-polyion configurations in the actual polyelectrolyte solutions to qualitatively reproduce the characteristic peak of the reduced viscosity appearing at lower concentrations.
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TL;DR: In this paper, the binding of an excess electron to HCN and HNC was studied at the coupled cluster level of theory with single, double, and noniterative triple excitations and with extended basis sets to accommodate the loosely bound excess electron.
Abstract: The binding of an excess electron to HCN and HNC was studied at the coupled cluster level of theory with single, double, and noniterative triple excitations and with extended basis sets to accommodate the loosely bound excess electron. The HCN molecule, with a dipole moment of 3.05 Debye, binds an electron by 10 cm−1, whereas the HNC tautomer possesses a similar dipole moment (3.08 Debye) and binds the electron by 43 cm−1. The electronic stability of the anionic system along the minimum energy HCN→HNC tautomerization path has been investigated, and it was concluded that the excess electron autodetaches during the tautomerization. Unusually large electron correlation energy contributions to the total electron binding energy were found and are discussed.
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TL;DR: This paper develops constitutive relations for materials where the magnetization and polarization may depend on both the electric and magnetic fields, and derives evolution equations for the displacement and induction fields from a Hamiltonian approach.
Abstract: In this paper we develop constitutive relations for materials where the magnetization and polarization may depend on both the electric and magnetic fields. The approach is general, and is based on a previously developed statistical-mechanical theory. We include the quadrupole-moment density as well as the dipole-moment density in the microscopic displacement field. This yields an electric gradient term in the constitutive equations. This leads to origin invariance in the multipole moments from which Maxwell's equations are defined. We present generalizations of Debye and Landau-Lifshitz equations of motion which are valid for nonequilibrium and contain memory. The reversible and relaxation terms in the polarization and magnetization evolution equations include the possibility of magnetoelectric coupling. Using constitutive relationship, we derive evolution equations for the displacement and induction fields from a Hamiltonian approach.
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TL;DR: In this paper, a class of systems characterized by the formation of transverse linear aggregates of particles is determined, where the aggregates are weakly conducting media with nonconducting particles but more polar than the medium.
Abstract: The electroosmotic component of the mutual dielectrophoresis is accounted for in the theory of the polarization interaction of uncharged particles. Previously, for the case when the polarization charge layer thickness is small as compared with the particle radius, it was shown that the electro-osmosis exerts significant effect on the motion of a particle in a nonuniform field (external or induced by a neighboring particle). The electro-osmosis in the induced Debye atmosphere of arbitrary thickness is considered in this paper. A class of systems characterized by the formation of transverse linear aggregates of particles is determined. The aggregates are weakly conducting media with nonconducting particles but more polar than the medium. The possibility of the occurrence of transverse electrocoagulation structures, which was originally obtained by us using the heuristic approach, is supported by results obtained in the solution of the electrohydrodynamic problem of the long-range interaction of polarized particles. The results obtained confirm high efficiency of the heuristic method used.
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TL;DR: The role of an external magnetic field via the ion polarization drift effect has been investigated theoretically on the dust-Coulomb crystal formation in a dusty plasma in the presence of continuous ion flows from the bulk plasma to the sheath as discussed by the authors.
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01 Dec 2001
TL;DR: In this paper, the Gaussian-Boltzmann equation of a spherical colloid particle has been solved under general potential condition by employing the iterative method in functional analysis, and the radius and the surface potential of a particle have been defined and the corresponding values have been estimated with the help of Newton's iterative methods.
Abstract: By employing the iterative method in functional analysis, the governing Poisson–Boltzmann equation of a spherical colloid particle that is based on the so-called Gouy–Chapman–Stern model has been solved under general potential condition. The solution of the potential in the second iteration is a function of the distance from the center of the particle with the concentration of ions, the temperature of system and the particle charge as parameters. From this solution the radius and the surface potential of a particle have been defined and the corresponding values have been estimated with the help of the Newton's iterative method. Based on the equivalent condenser model with the same center of the particle, the correlation among the electric double layer thickness, the radius and the surface potential has been established. The analysis of the quartic equation of the thickness shows that it has a sole positive real root which is much more reasonable than the Debye reciprocal length from the Debye–Huchel approximation to represent the thickness. The calculation of the thickness can be much simplified in case of a higher concentration of ions or a higher particle charge.
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TL;DR: In this article, the electron temperature gradient (ETG) driven drift mode is studied using an advanced fluid model retaining effects of nonadiabatic ions, Debye shielding and the electron diamagnetic heat flow.
Abstract: The electron temperature gradient (ETG) driven drift mode is studied using an advanced fluid model retaining effects of nonadiabatic ions, Debye shielding and the electron diamagnetic heat flow. The derived eigenmode equation is solved analytically in the strong ballooning limit. Both the toroidal and the slab branch of the ETG mode are included and the fluid growth rates are compared with gyrokinetic results. The role of nonadiabatic ion response is found to have a stabilizing effect on ETG-mode in the lower-hybrid regime. Strong stabilization is also found due to Debye shielding effect for λDe2/ρe2>1. In particular, it is shown that nonadiabatic ion response can result in inward flows of particles for peaked density profiles.
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TL;DR: In this paper, the Debye-Waller factors associated with the two principal directions are equal within the limits of experimental errors, and the energy of formation of vacancies (Ef) has been estimated from a semi-empirical relation between Ef and θ.
Abstract: Debye–Waller factors of five h.c.p. elements (Ti, Zr, Ru, Tm, Hf) have been determined from X-ray diffraction intensities. Within the limits of experimental errors, the Debye–Waller factors associated with the two principal directions are equal. The Debye temperatures (θM) have been evaluated. The energy of formation of vacancies (Ef) has been estimated from a semi-empirical relation between Ef and θ.
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TL;DR: Algebraic simplifications are developed for calculating multiplicities in the double summation and used in a new algorithm for implementing this equation, which gives the spherically averaged diffracted intensity from a group of atoms.
Abstract: The Debye equation gives the spherically averaged diffracted intensity from a group of atoms and is exact under the first Born, or kinematic, approximation. Algebraic simplifications are developed for calculating multiplicities in the double summation and are used in a new algorithm for implementing this equation. The results for cubic, body-centred cubic and face-centred cubic systems agree exactly with previous methods while achieving substantial computational advantage.
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TL;DR: In this paper, the SU(3) gauged 2D model for adjoint scalar fields, defined by dimensional reduction of pure gauge QCD in (2 + 1)D at high temperature, is presented.
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TL;DR: In this paper, the authors investigated the dielectric properties of a structurally disordered insulator in the framework of a theoretical model consisting of a self-similar structure composed of Debye relaxators.
Abstract: Dielectric properties of a structurally disordered insulator were investigated in the framework of a theoretical model. The model consists of a self-similar structure composed of Debye relaxators which describes a system with a wide distribution of relaxation times that exhibits power-law relaxation at high frequencies in constant temperature measurements. The analysis of the correspondent behavior in a thermally stimulated depolarization experiment shows that the current in the low temperature side of the depolarization peak displays a power-law dependence on heating rate which is a consequence of the self-similar property of the system. The fractionary power-law is related to the fractal dimension by a=2(1−D/3). Therefore the analysis establishes the correlation between isothermal and nonisothermal measurements in dielectric materials that exhibit quasiuniversal nonexponential relaxation.
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TL;DR: The electron temperature gradient driven instabilities in plasmas with slightly hollow density profiles are studied in this article, where the gyrokinetic integral eigenvalue equation valid for a sheared slab configuration is employed.
Abstract: The electron temperature gradient driven instabilities in plasmas with slightly hollow density profiles are studied. The gyrokinetic integral eigenvalue equation valid for a sheared slab configuration is employed. The Debye shielding effect on the modes is investigated. The effects of a sheared E×B flow on the modes are considered. Six modes with even or odd parities are found to be simultaneously unstable. The mixing length estimate for the transport is calculated. The flow shear suppression on the modes, as well as on the transport, is demonstrated. The correlations of the results with helical system Heliotron/Torsotron and tokamak experiments are discussed.
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TL;DR: In this article, different numerical schemes were implemented to simulate the Schrodinger-Debye equations that occur in nonlinear optics, and the convergence of the methods was proved and simulations seem indeed to show that for at least small delays self-focusing solutions may exist.
Abstract: In this article we implement different numerical schemes to simulate the Schrodinger-Debye equations that occur in nonlinear optics. Since the existence of blow-up solutions is an open problem, we try to compute such solutions. The convergence of the methods is proved and simulations seem indeed to show that for at least small delays self-focusing solutions may exist.
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30 Mar 2001
TL;DR: In this article, a numerical technique is proposed to derive the Debye coefficients from the measured frequency-dependent permittivity of different biological tissues, and then a scattered field FDTD formulation is developed for such dispersive media characterized by multi-term Debye expressions.
Abstract: For practical bio-electromagnetic applications, such as the interaction of electromagnetic fields with the human head and body, accurate simulation of biological tissues is a key factor for reliable results. The characteristics of biological tissues are frequency dependent and thus called dispersive materials. For accurate FDTD simulation of biological tissues, a numerical technique is proposed to derive the Debye coefficients from the measured frequency-dependent permittivity of different biological tissues, and then a scattered field FDTD formulation is developed for such dispersive media characterized by multi-term Debye expressions. The proposed scattered field FDTD formulation is valid for three dimensional analysis of practical EM problems involving combination of dispersive and non-dispersive materials. The developed procedure has been verified for different types of biological tissues over a very wide band of frequency (from 30 Hz to 20 GHz). The reflection coefficients of a semi-infinite dispersive medium using one, two, and three-term Debye expressions are computed and compared favorably with the corresponding analytical solution. Hence, the accuracy and stability of modeling multi-term Debye dispersive materials using the proposed scattered FDTD formulation is assessed.
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TL;DR: In this article, a finite-length diocotron mode for a non-neutral plasma column under the assumption of bounce averaged E×B drift dynamics and small Debye length is discussed.
Abstract: Diocotron modes are discussed for a finite length nonneutral plasma column under the assumption of bounce averaged E×B drift dynamics and small Debye length. In this regime, which is common to experiments, Debye shielding forces the mode potential to be constant along field lines within the plasma (i.e., ∂δφ/∂z=0). One can think of the plasma as a collection of magnetic-field aligned rods that undergo E×B drift across the field and adjust their length so as to maintain the condition ∂δφ/∂z=0 inside the plasma. Using the Green function (for a region bounded by a conducting cylinder) to relate the perturbed charge density and the perturbed potential, imposing the constraint ∂δφ/∂z=0, and discretizing yields a matrix eigenvalue problem. The mode eigenvector δNl,ω(rj)≡∫dz δnl,ω(rj,z) is the lth azimuthal Fourier component of the z-integrated density perturbation, and the frequency ω is the eigenvalue. The solutions include the full continuum and discrete stable and unstable diocotron modes. Finite column leng...