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Full-Text Articles in Physical Sciences and Mathematics
Decay Of Molecules At Spherical Surfaces: Nonlocal Effects, P.T. Leung
Decay Of Molecules At Spherical Surfaces: Nonlocal Effects, P.T. Leung
Physics Faculty Publications and Presentations
The decay rates for molecules in the vicinity of a metallic sphere are investigated in a phenomenological approach for very close molecule-surface distances d. The Fuchs-Claro model [Phys. Rev. B 35, 3722 (1987)] is adopted to describe the polarizability of the sphere with the nonlocal dielectric response being accounted for within the hydrodynamic description. The results show significant differences when compared with those obtained previously within a local description for dlsim50 Aring, with extra resonances observed in the high-frequency regime, a phenomenon similar to that noted previously by Ruppin (1982), in his calculation of the extinction cross section for such …
Dielectric Constant In Fluids Of Classical Deformable Molecules, John D. Ramshaw
Dielectric Constant In Fluids Of Classical Deformable Molecules, John D. Ramshaw
Physics Faculty Publications and Presentations
Classical statistical mechanical description of dielectric fluids is further discussed. Dipole moment correlations of polarizable molecules are discussed.
Existence Of The Dielectric Constant In Fluids Of Classical Deformable Molecules, John D. Ramshaw
Existence Of The Dielectric Constant In Fluids Of Classical Deformable Molecules, John D. Ramshaw
Physics Faculty Publications and Presentations
The existence of the dielectric constant epsilon is investigated for fluids composed of classical deformable (polarizable) molecules. The development is based upon generalized functional-derivative relations which involve joint distributions in molecular positions r/sub k/ and dipole moments ..mu../sub k/. Sufficient conditions for the existence of epsilon are expressed in terms of the generalized direct correlation function c(12) = c(r/sub 1/, ..mu../sub 1/; r/sub 2/, ..mu../sub 2/). It is found that epsilon exists if -kTc(12) depends only on relative positions and dipole moment directions (in addition to Vertical Bar..mu../sub 1/Vertical Bar and Vertical Bar..mu../sub 2/Vertical Bar), and becomes asymptotic to the …
Existence Of The Dielectric Constant In Dipolar Fluid Mixtures, John D. Ramshaw, Norman D. Hamer
Existence Of The Dielectric Constant In Dipolar Fluid Mixtures, John D. Ramshaw, Norman D. Hamer
Physics Faculty Publications and Presentations
The existence of the dielectric constant epsilon is investigated for fluid mixtures of rigid polar molecules. The investigation is performed using the functional-derivative formalism for mixtures, and is closely analogous to that previously carried out for pure dipolar fluids (J. Chem. Phys. 68, 5199 (1978)). Sufficient conditions for the existence of epsilon are obtained in terms of the direct correlation function matrix c/sub alphabeta/(12). It is found that epsilon exists if c/sub alphabeta/(12) depends only on relative positions and orientations, and becomes asymptotic to -theta/sub alphabeta/(12)/kT at long range, where theta/sub alphabeta/(12) is the dipole--dipole potential between a molecule of …
Dielectric Saturation In Dipolar Fluids. I. The Single-Molecule Distribution Function, John D. Ramshaw
Dielectric Saturation In Dipolar Fluids. I. The Single-Molecule Distribution Function, John D. Ramshaw
Physics Faculty Publications and Presentations
The functional-derivative formalism is used to investigate the form of the equilibrium single-molecule distribution function n(1) in a finite fluid system of rigid polar molecules subjected to a strong external electric field that varies slowly with position. The investigation is based on the assumption that the long-range asymptotic behavior of the direct correlation function is independent of the external field, and is hence the same as in the unperturbed fluid. This assumption implies that n(1) has the form of a single-molecule Boltzmann factor in which the interaction energy is that of a deformable quasidipole with the local Lorentz electric field …
Debye–Hückel Theory For Particles Of Arbitrary Electrical Structure, John D. Ramshaw
Debye–Hückel Theory For Particles Of Arbitrary Electrical Structure, John D. Ramshaw
Physics Faculty Publications and Presentations
Classical linearized Debye–Hückel theory is formulated for a finite fluid system, of arbitrary shape, composed of rigid particles with arbitrary internal electrical structure. The multipole description is eschewed in favor of the more basic description of a particle in terms of its charge density function. This function is left arbitrary, so the particles may be charged or neutral, polar or nonpolar, etc. The theory implies that the direct correlation function c(12)=−v(12)/k T, where v(12) is the Coulomb interaction energy between the charge densities of particles 1 and 2. In the case of uncharged polar …
Comments On The Theory Of Dipolar Fluids, John D. Ramshaw
Comments On The Theory Of Dipolar Fluids, John D. Ramshaw
Physics Faculty Publications and Presentations
The theory of dipolar fluids posbulated by Chan, Mitchell and Ninham is commented upon.
Existence Of The Dielectric Constant In Fluids Of Nonlinear Rigid Polar Molecules, John D. Ramshaw
Existence Of The Dielectric Constant In Fluids Of Nonlinear Rigid Polar Molecules, John D. Ramshaw
Physics Faculty Publications and Presentations
The existence of the dielectric constant epsilon is investigated for fluids composed of nonlinear rigid polar molecules. The investigation is performed using the functional-derivative approach previously employed to establish sufficient conditions for the existence of epsilon in fluids of linear (axially symmetric) molecules. It is shown that these same conditions are sufficient for nonlinear molecules of arbitrary symmetry. An expression for epsilon in terms of the direct correlation function emerges automatically from the development. This expression, which involves the inversion of a 3 x 3 matrix, is a slight generalization of one obtained earlier by Hoye and Stell using an …
Existence Of The Dielectric Constant In Rigid-Dipole Fluids: The Functional-Derivative Approach, John D. Ramshaw
Existence Of The Dielectric Constant In Rigid-Dipole Fluids: The Functional-Derivative Approach, John D. Ramshaw
Physics Faculty Publications and Presentations
In a previous article [J. Chem. Phys. 57, 2684 (1972)] sufficient conditions were established for the existence of the dielectric constant ɛ in rigid-dipole fluids. One of these conditions was an unrealistic restriction on the angular dependence of the direct correlation function c (12) at short range. Here it is shown that this restriction can be removed without altering the previous conclusions. Consequently, ɛ rigorously exists if c (12) depends only upon relative positions and orientations of molecules 1 and 2, and becomes asymptotic to -φd(12)/kT at long range, where φd(12) is the dipole-dipole potential. The development is based upon …
On The Reduction Of Many-Body Dielectric Theories To The Onsager Equation, John D. Ramshaw
On The Reduction Of Many-Body Dielectric Theories To The Onsager Equation, John D. Ramshaw
Physics Faculty Publications and Presentations
An approximate theory for the dielectric constant ℇ of a dense polar fluid was derived by Ramshaw, Schaefer, Waugh, and Deutch (RSWD). In the present article, the RSWD theory is generalized and made rigorous by another method of derivation. The result is a rigorous expression for ℇ which differs from the RSWD expression by the presence of a fluctuation term. Both the rigorous expression and the RSWD expression are then specialized to the Onsager model. It is found that the rigorous expression for ℇ reduces to the Onsager equation, but that the RSWD expression does not because the fluctuation term …
Existence Of The Dielectric Constant In Rigid-Dipole Fluids: The Direct Correlation Function, John D. Ramshaw
Existence Of The Dielectric Constant In Rigid-Dipole Fluids: The Direct Correlation Function, John D. Ramshaw
Physics Faculty Publications and Presentations
The question of whether the dielectric constant ε exists (is well defined) for a finite fluid system of rigid dipolar molecules is reconsidered and reformulated. It is found that this question can most simply be expressed in terms of the behavior of the position‐ and orientation‐dependent direct correlation function c(r1,ω1; r2, ω2). It is shown that ε exists if c satisfies the following two conditions: (a) c~–φ/kT for |r1–r2|>σ, where φ is the dipole‐dipole potential and σ is a length which is large microscopically but small macroscopically. …
On The Molecular Theory Of Dielectric Polarization In Rigid‐Dipole Fluids, John D. Ramshaw
On The Molecular Theory Of Dielectric Polarization In Rigid‐Dipole Fluids, John D. Ramshaw
Physics Faculty Publications and Presentations
A molecular theory is developed for the polarization P(r) produced by a weak position‐dependent external electric field E0(r) in a finite fluid system, of arbitrary shape, composed of rigid polar molecules. The theory differs from earlier work in that no assumption is made concerning the form of the electrostatic constitutive relation. [The usual assumption in this regard is that P(r) = (ε–1) E(r) / 4π, where E(r) is the total Maxwell electric field. The “dielectric constant” ε is well defined only if the relation between P(r) and E(r) …
Dielectric Polarization And Alignment And The Structure Of Polar Fluids, John D. Ramshaw, D. W. Schaefer, John S. Waugh, J. M. Deutsch
Dielectric Polarization And Alignment And The Structure Of Polar Fluids, John D. Ramshaw, D. W. Schaefer, John S. Waugh, J. M. Deutsch
Physics Faculty Publications and Presentations
An analysis is made of the information about the structure of dense polar fluids which resides in the dielectric constant, the Kerr constant, and the nuclear magnetic resonance (NMR) quadratic electric field effect. The inadequacy of the "local-field" model for liquids is discussed. The existence of a nonzero molecular hyperpolarizability is shown to destroy an equivalence which would otherwise exist between the Kerr and NMR experiments, and can easily account for apparent discrepancies between the reported Kerr and NMR data for nitrobenzene and nitromethane. A method is presented for removing dielectric boundary effects from statistical averages, so that the averages …