Showing papers on "Dipole published in 1983"
TL;DR: In this article, the integral equation for the polarization of a macroscopic dielectric in an arbitrary external field, is written in a form that allows explicit inclusion of the toroidal boundary conditions as well as the cutoff of dipolar interactions often used in the computer simulation of polar systems.
Abstract: The fundamental equation of electrostatics, i.e. the integral equation for the polarization of a macroscopic dielectric in an arbitrary external field, is written in a form that allows explicit inclusion of the toroidal boundary conditions as well as the cutoff of dipolar interactions often used in the computer simulation of polar systems. The toroidal boundary conditions are accounted for in a natural way if the integral equation is formulated (and solved) in Fourier space. Rigorous expressions for the polarization induced by a homogeneous field as well as for the equilibrium dipole moment fluctuations, both as a function of the dielectric constant, are then easily derived for general systems in two and three dimensions. The equations obtained for spherical cutoff geometry with reaction field are identical to those valid for an infinite periodic system (Ewald sum plus reaction field). When applied to the case of a highly polar Stockmayer system (μ*2=3·0, θ*=0·822, T*=1·15) the formulas lead to a consiste...
598 citations
TL;DR: In this article, a collection of Rydberg atoms and a resonant millimeter-wave cavity were shown to exchange energy back and forth at a rate of 2π(n σ(n) σ + σ 2 σ − σ σ n/n/n), where n is the electric dipole matrix element of the atomic transition and σ is the field per photon in the cavity.
Abstract: A collection of $N$ Rydberg atoms and a resonant millimeter-wave cavity are shown to exchange energy back and forth at a rate $2(\frac{d}{\ensuremath{\hbar}}){\mathcal{E}}_{0}\sqrt{N}$, where $d$ is the electric dipole matrix element of the atomic transition and ${\mathcal{E}}_{0}$ the "field per photon" in the cavity. This experiment is a demonstration of self-induced Rabi oscillations in a two-level atom system coupled to a single electromagnetic field mode and can also be considered as a very simple illustration of "ringings" in superradiant emission.
362 citations
TL;DR: The spherical model can now be used with more confidence to predict differences in neural sources which cannot be approximated by a dipole, and the MEG-EEG differences will depend on the particular case.
298 citations
TL;DR: In this paper, the first direct microscopic observations of the crystallization of magnetic holes forming a variety of different lattices were presented, showing that the apparent dipolar interactions between the spheres may be made attractive or repulsive.
Abstract: Holes are produced inside a thin layer of magnetic fluid with use of monodisperse polystyrene spheres with diameters in the micrometer range. With an external magnetic field an apparent magnetic dipole will be associated with each hole as a result of the displaced fluid. The apparent dipolar interactions between the spheres may be made attractive or repulsive. This Letter presents the first direct microscopic observations of the crystallization of magnetic holes forming a variety of different lattices.
289 citations
TL;DR: In this article, the electric dipole moment of the neutron in models with low energy supergravity or softly broken supersymmetry was computed, typically of order 10−(22−23) e cm times CP-violating phaes.
233 citations
TL;DR: Theoretical values of electric and magnetic susceptibilities ( α 1, α 2, χ 1 ) and shielding factors ( γ 1, γ 2, 1 ) calculated in the relativistic random-phase approximation are presented in tabular form for ions with closed 1 s, 2 p, 3 p, 4 d, 4 p, 4 d, and 5 p shells.
230 citations
TL;DR: In this paper, the permanent dipole moments of excited molecules can be obtained from the ratio of the solvent shifts of absorption and fluorescence spectra, which eliminates the uncertain solute cavity radius parameter, as well as the solvent polarity function.
221 citations
TL;DR: In this paper, the distribution of current in and the admittance of a center-driven dipole embedded in a general medium are reviewed, and the electric field generated by the currents in the dipole is derived for all points outside the antenna.
Abstract: Insulated antennas are useful for localized heating as in the hyperthermia treatment of tumors and the extraction of shale oil. The distribution of current in and the admittance of a center-driven dipole embedded in a general medium are reviewed. Formulas for the electric field generated by the currents in the dipole are derived for all points outside the antenna. Near the antenna, the field is elliptically polarized. Formulas for the polarization ellipses are derived and evaluated for antennas with electrical half-lengths Beta/sub L/h = pi/4, pi/2, pi, and 3pi/2, where k/sub L/ =beta/sub L/ + i alpha/sub L/ is the wavenumber of the current, and this is different from the wavenumber of the ambient medium.
214 citations
TL;DR: In this article, the effect of surface waves on dipole and slot elements on substrates was considered and the radiation and bandwidth of microstrip dipoles were optimized in terms of substrate thickness and permittivity.
Abstract: The reciprocity theorem and integral equation techniques are employed to determine the properties of integrated-circuit antennas. The effect of surface waves is considered for dipole and slot elements on substrates. The radiation and bandwidth of microstrip dipoles are optimized in terms of substrate thickness and permittivity.
210 citations
187 citations
Patent•
21 Nov 1983TL;DR: In this article, an electric dipole current source is towed from a survey vessel in a body of water substantially parallel to the surface of the body of waters and separated from the floor by a distance less than approximately one-quarter of the distance between the surface and the floor.
Abstract: An improved method and apparatus for electromagnetic surveying of a subterranean earth formation beneath a body of water. An electric dipole current source is towed from a survey vessel in a body of water substantially parallel to the surface of the body of water and separated from the floor of the body of water by a distance less than approximately one-quarter of the distance between the surface and the floor. Alternating electric current, preferably including a plurality of sinusoidal components, is caused to flow in the source. An array of electric dipole detectors is towed from the survey vessel substantially collinearly with the current source. Each electric dipole detector of the array is separated from the current source by a distance substantially equal to an integral number of wavelengths of electromagnetic radiation, of frequency equal to that of a sinusoidal component of the source current, propagating in the water. A gradient detector array is also towed by the survey vessel in a position laterally separated from, or beneath, the mid-point of the current source. Additionally, an array of three-axis magnetic field sensors mounted in controllable instrument pods are towed by the seismic vessel on the flanks of the current source. Frequency-domain and time-domain measurements of magnetic and electric field data are obtained and analyzed to permit detection of hydrocarbons or other mineral deposits, or regions altered by their presence, within subfloor geologic formations covered by the body of water.
TL;DR: In this article, the potential energy and dipole moment functions for ground states of OH, OH−, and OH+ have been calculated from MCSCF, MCSC-SCEP, and SCEP-CEPA electronic wave functions.
Abstract: Potential energy and dipole moment functions for the ground states of OH, OH−, and OH+ have been calculated from MCSCF, MCSCF‐SCEP, and SCEP‐CEPA electronic wave functions. The stability of the dipole moments with respect to the number of configurations (up to 598) and orbitals (up to 14) simultaneously optimized in the MCSCF procedure and the number of reference configurations (up to 11) in the MCSCF‐SCEP wave functions (up to 69 830 configurations) has been investigated. The dipole moment functions obtained from the best electronic wave functions are more accurate than all previously calculated ones. The deficiencies of the former calculations have been critically analyzed. The OH− and OH+ ions are predicted to be stronger IR emitters than the neutral OH radical. The rotationless rates of spontaneous emission A10 for the fundamental transitions are calculated to be 12.2, 137, and 263 s−1 for OH, OH−, and OH+, respectively. The calculated dipole moments in the vibrational ground states are 1.65, 1.04, an...
TL;DR: In this paper, three orthogonal dipoles are used in an E-field probe to provide a response which is nearly isotropic for all polarizations of the incident field.
Abstract: Electric field probes consisting of a dipole antenna, RF detector, nonperturbing transmission line, and readout device have been implemented in a variety of ways. Three orthogonal dipoles are generally used in an E -field probe to provide a response which is nearly isotropic for all polarizations of the incident field. Diode detectors have been used with electrically short or resistivity loaded dipoles to produce very broadband devices (0.2 MHz to 26 GHz). Thermocouple detectors are used to provide true time-averaged data for high peak-power modulated fields. Optical fibers, together with a suitably modulated light source, may be used to form a wide-band nonperturbing data link from the dipole and detector to a remote readout. Application of E -field probes range from the measurement of fields in living animals exposed to nonionizing radiation to the measurement of fields in air for electromagnetic compatability or radiation safety purposes. Probes are available that can measure field strengths from less than 1 V/m to over 1000 V/m (rms).
TL;DR: In this paper, the microwave spectra of nine isotopic species of borane monoammoniate (11BH3NH3, 10BH 3 NH3, 11BD2HNH3 and 11BD3ND2H) have been observed and the rotational constants, centrifugal distortion constants, dipole moment, torsional barrier, and molecular geometry of BN were determined from these spectra.
Abstract: The microwave spectra of nine isotopic species of borane monoammoniate (11BH3NH3, 10BH3NH3, 11BH3ND3, 10BH3ND3, 11BD3NH3, 11BH3 15NH3, 10BH3 15NH3, 11BD2HNH3, 11BH3ND2H) have been observed. The rotational constants, centrifugal distortion constants, dipole moment, torsional barrier, and molecular geometry of borane monoammoniate were determined from these spectra. The rs structure is: BN=1.6576(16) A, BH=1.2160(17) A, NH=1.0140(20) A, ∠NBH=104.69(11), ∠BNH=110.28(14). The dipole moment is 5.216(17) D. The torsional barrier about the B–N bond, V3, is 2.047(9) kcal mol−1 for 11BH3ND2H and 2.008(4) kcal mol−1 for 11BD2HNH3.
TL;DR: In this paper, a quantum mechanical method based on the Kramers-Heisenberg dispersion relation is used to evaluate the dielectric response of small metal particles, and thereby to determine the influence of particle size on the widths of the plasmon resonance line shapes.
Abstract: A quantum mechanical method based on the Kramers–Heisenberg dispersion relation is used to evaluate the dielectric response of small metal particles, and thereby to determine the influence of particle size on the widths of the plasmon resonance line shapes. Several different particle shapes are considered (sphere, cylinder, rectangular prism, spherical shell, and cylindrical shell) and for each shape a free electron Schrodinger equation is used to determine conduction band energies and dipole matrix elements. The main emphasis in this work is on particle sizes large enough that only the first order deviations from the infinite size limit are important, and for such sizes we find that the size dependent contribution to the width can be expressed in terms of an effective length Leff. This effective length is found to depend on the direction of the external field relative to the particle symmetry axes, and on the shape of the particle. For compact shapes, Leff is accurately approximated by 0.65 Lav along eac...
TL;DR: In this article, the optical birefringence induced by an electric field-gradient has been measured in the four non-polar gases nitrogen, ethane, cyclopropane and chlorine, and in the two polar gases nitrous oxide and methyl fluoride.
Abstract: The optical birefringence induced by an electric field-gradient has been measured in the four non-polar gases nitrogen, ethane, cyclopropane and chlorine, and in the two polar gases nitrous oxide and methyl fluoride Together with known values of the anisotropy in molecular polarizability, the measurements on the non-polar molecules yield the electric quadrupole moments Θ = -4·90 ± 0·3 × 10-40 C m2 for nitrogen, -3·34 ± 0·13 × 10-40 C m2 for ethane, 5·3 ± 0·7 × 10-40 C m2 for cyclopropane and 10·79 ± 0·54 × 10-40 C m2 for chlorine In polar molecules the measured birefringence arises not only from the quadrupole moment, but also from the higher polarizabilities describing the electric dipole induced by an electric field-gradient and a time-varying magnetic field This additional contribution is shown to be small in the case of nitrous oxide, but in methyl fluoride it predominates
TL;DR: In this article, the minimum free energy and the equilibrium solute and defect distributions in the grain-boundary region were evaluated. And the authors identified the interaction potentials between solute ions and grain boundaries.
Abstract: The interaction potentials between solute ions and grain boundaries in ionic solids are identified as (1) the electrostatic interaction between the charged solutes and grain boundaries, (2) the elastic energy due to the size misfit of solutes in the matrix, and (3) the dipole interactions between the solute‐vacancy dipoles and the electric field in the grain‐boundary region. We include these interaction potentials to evaluate the minimum free energy and the equilibrium solute and defect distributions in the grain‐boundary region. Numerical calculations show that these interaction mechanisms, either acting individually or coupling with each other, lead to a nonuniform solute distribution near the grain boundary. Under certain conditions, both the elastic and dipole interactions can significantly modify the electrostatic potential near the boundary. Calculations also show that the grain‐boundary segregation of an aliovalent solute can be induced or altered by another aliovalent solute of different size misfit with the matrix.
TL;DR: In this article, the authors studied the collective effects between spin-glasses with different amounts of Li and showed that these collective effects occur below a fairly well-defined concentration-dependent temperature of the order of 50 K.
Abstract: Li, substituting for K in KTa${\mathrm{O}}_{3}$, creates a local electric dipole, due to its off-center position with respect to the cubic site. We have studied such crystals with different amounts of Li (and in a few cases also doped with Nb, substituting for Ta) by nuclear magnetic resonance, dielectric relaxation, pyroelectricity, ultrasound, and birefringence methods. Birefringence and dielectric susceptibility results show that collective effects between the Li dipoles occur below a fairly well-defined concentration-dependent temperature of the order of 50 K, but nuclear magnetic and dielectric relaxation indicate the absence of criticality at the onset of these effects. These collective effects are related to those arising in spin-glasses. We discuss the data in the light of theoretical models and computer simulations of systems of randomly interacting moments, which predict an apparent condensation into a system of metastable clusters without long-range order.
TL;DR: In this article, a perturbation theory to account for anisotropic long-ranged terms is described, giving two dið-electric constant estimates from one simulation, and the results are illustrated with Monte Carlo simulations of the Stockmayer system at reduced density 0.8, reduced square dipole moment 2.0 and scaled temperature 1.35.
Abstract: This paper makes some developments and clarifications of the theory for the application of periodic boundary conditions to the numerical simulation of the statistical mechanics of a cubic sample of dipolar particles. The reaction-field effect is treated rigorously. The anisotropies inherent in the periodic boundary condition Hamiltonian are allowed for in the derivation of a new fluctuation formula. A perturbation theory to account for anisotropic long-ranged terms is described, giving two di-electric constant estimates from one simulation. These new results are illustrated with Monte Carlo simulations of the Stockmayer system at reduced density 0.8, reduced square dipole moment 2.0 and scaled temperature 1.35, giving a dielectric constant estimate of 25 ± 2 from all the data, and showing that the perturbation theories are very accurate. It appears possible to claim that periodic boundary conditions should be used with infinite external dielectric constant in almost all circumstances, because they then give a chain of configurations that provide comparatively very stable estimates of dielectric constant.
TL;DR: In this article, the dipole moment matrix elements have been computed for the five most abundant isotopes of CO. The wave functions utilized were obtained from a direct solution of the Schrodinger equation with an accurate RKR potential.
TL;DR: In this article, the authors discuss the use of variations de champ electrique induit sur des spectres d'absorption for determiner des polarisabilites and des moments dipolaires a l'etat excite.
Abstract: utilisation de variations de champ electrique induit sur des spectres d'absorption pour determiner des polarisabilites et des moments dipolaires a l'etat excite, pour les diphenylbutadiene, diphenylhexatriene, diphenyloctatetraene, diphenyldecapentaene et le retinal tout-trans
TL;DR: In this paper, a source of CP violation in supersymmetric theories is discussed, and the effect of such violations on the electric dipole moment of the electron and the neutron is estimated.
TL;DR: In this paper, the parity and CP-nonconserving interaction in the QCD Lagrangian was studied, and the mixing of nearly degenerate opposite-parity ground-state doublets in certain deformed nuclei leads to electric dipole and magnetic quadrupole moments 10/sup 1/--10/sup 3/ and 10/Sup 3/6/4/4 times larger than those generated by the unpaired valence nucleon.
Abstract: T- and P-nonconserving nuclear moments induced by a parity- and CP-nonconserving interaction in the QCD Lagrangian are discussed. The mixing of nearly degenerate opposite-parity ground-state doublets in certain deformed nuclei leads to electric dipole and magnetic quadrupole moments 10/sup 1/--10/sup 3/ and 10/sup 3/--10/sup 4/ times larger, respectively, than those generated by the unpaired valence nucleon.
TL;DR: In this article, a general parametrization scheme for the electric dipole intensities of lanthanide 4f → 4f crystal field transitions is proposed. But it does not consider the effects of ligand polarizability anisotropy on the intensity parameters.
Abstract: A general parametrization scheme for the electric dipole intensities of lanthanide 4f → 4f crystal‐field transitions is proposed. This parametrization is sufficiently general to accommodate any 4f → 4f intensity mechanism based on the ‘‘one‐electron’’ and ‘‘one‐photon’’ approximations for lanthanide‐ligand‐radiation field interactions. It includes as a subset, the familiar Judd–Ofelt–Axe intensity parameters, AtpΞ(t, λ), but introduces additional parameters which are shown to be essential in cases where the lanthanide‐ligand pairwise interactions cannot be assumed to be cylindrically symmetric. Expressions are given for calculating the general intensity parameters in terms of two specific intensity mechanisms. Special consideration is given to the effects of ligand polarizability anisotropy on the intensity parameters. A set of ‘‘intrinsic’’ intensity parameters are also introduced. These parameters are defined within the context of the ‘‘superposition’’ model for lanthanide‐ligand interactions, and are i...
TL;DR: In this article, the authors obtained analytical solutions in the time domain for the electric and magnetic fields associated with establishing a finite electrostatic dipole, assuming that a simple source current distribution, a square pulse of current, produces the dipole.
Abstract: We obtain analytical solutions in the time domain for the electric and magnetic fields associated with establishing a finite electrostatic dipole. We assume that a simple source current distribution, a square pulse of current, produces the dipole, and solve for the fields produced by that source current distribution using Maxwell’s equations. Salient features of the fields are discussed from a physical point of view. We outline a technique to determine in the time domain the electric and magnetic fields produced by any arbitrary time‐varying current propagating along a straight antenna, given the calculated fields due to a short square pulse of current.
TL;DR: In this article, a microscopic correlation function theory for coherent, parametric, four-photon processes (four-wave mixing) and for single-absorber two-photons processes (twophoton absorption, Raman, and fluorescence spectra) is developed.
Abstract: A microscopic correlation-function theory for coherent, parametric, four-photon processes (four-wave mixing) and for single-absorber two-photon processes (two-photon absorption, Raman, and fluorescence spectra) is developed. Both types of experimental observables are expressed in terms of four-point correlation functions of the dipole operator. The latter are then evaluated semiclassically or within the factorization approximation in which they are expressed in terms of ordinary single-photon line-shape functions. The common results of the Bloch equations are shown to be the outcome of two successive approximations: the factorization approximation and the impact limit whereby the single-photon line-shape functions are taken to be Lorentzian. Effects of fluctuations in the radiation fields are easily incorporated within the present approach.
TL;DR: The effects of torso inhomogeneities on electrocardiographic potentials were investi-gated via computer simulation, using a 23-dipole heart model placed within a realistically shaped human torso model to confirm the validity of the "Brody effect" and large quantitative effects on the surface potentials.
Abstract: The effects of torso inhomogeneities on electrocardiographic potentials were investigated via computer stimulation, using a 23-dipole heart model placed within a realistically shaped human torso model. The transfer coefficients relating the individual dipoles to the torso surface potentials, as well as the body surface potential maps, the vectorcardiogram, and the 12-lead electrocardiogram resulting due to normal activation of the heart model, were calculated for each of the following torso conditions: homogeneous, homogeneous + skeletal muscle layer, homogeneous + muscle layer + lungs, and homogeneous + muscle layer + lungs + intraventricular blood masses. The effects of each inhomogeneity were deduced by comparing results before and after its inclusion. For individual dipole transfer coefficients we confirm the validity of the "Brody effect," whereby the high conductivity blood masses augment radially oriented dipoles and diminish tangentially oriented ones. With regard to the vectorcardiogram , the electrocardiogram, and the body surface potential maps, the major qualitative effects were an augmentation of the head-to-foot component of the vectorcardiogram due to the lungs, and a smoothening of notches in the electrocardiogram (temporal filtering) and of isopotential contours in the body surface potential maps (spatial filtering) with a consequent loss of information, due to the blood masses, muscle layer, and, to a lesser extent, the lungs. Besides the above qualitative effects of the inhomogeneities, there were also large quantitative effects on the surface potentials, namely, magnitude increases due to the blood masses and magnitude decreases due to the muscle layer, that--if unaccounted for--could compromise the inverse solution of these potentials for the cardiac dipole sources.
TL;DR: In this article, the effects of polarisation and exchange in low-energy elastic scattering of electrons from noble gases were studied and the authors concluded that including only the dipole part of the polarisation potential and treating exchange exactly produces the most reliable results.
Abstract: The authors continue their earlier study on the effects of polarisation and exchange in low-energy elastic scattering of electrons from noble gases. They present detailed results for argon and conclude that including only the dipole part of the polarisation potential and treating exchange exactly produces the most reliable results. The behaviour for neon is also very similar to that for helium. Values for phaseshifts, differential, total elastic and momentum transfer cross sections are given for neon and argon and compared with recent experimental and theoretical results.
TL;DR: In this article, the authors derived an equation which relates the dipole moment fluctuations observed in computer simulations of polar systems to the frequency-dependent dielectric constant, provided that the modified dipolar interactions do not explicitly depend upon time.
Patent•
23 Sep 1983TL;DR: In this paper, a bias means consisting of a plurality of dipole ring magnets, each of which is an oriented, anisotropic permanent magnet material, arranged in a ring so that there is a substantially continuous ring of magnet material.
Abstract: An NMR imaging apparatus (10) having a desired imaging volume for imaging of biological tissue, said apparatus comprising bias means (20) for generating a bias field, means for generating gradient fields, and radio frequency means for applying a pulse of electromagnetic radiation to the biological tissue and for detecting the resultant signals emitted from said tissue; wherein said bias means comprises a plurality of dipole ring magnets, (20) each dipole ring magnet comprising a plurality of segments, (22) each segment comprising an oriented, anisotropic permanent magnet material (23) arranged in a ring so that there is a substantially continuous ring of permanent magnet material; wherein the inner radius of at least one dipole ring magnet is different from the inner radius of an adjacent dipole ring magnet.