Showing papers on "Dipole published in 1974"

An empirical correlation of second virial coefficients

Abstract: A new correlation of second virial coefficients of both polar and nonpolar systems is presented. It uses the Pitzer-Curl correlation for nonpolar compounds, but in a modified form. The second virial coefficient of nonhydrogen bonding compounds (ketones, acetaldehyde, acetonitrile, ethers) and weakly hydrogen bonding compounds (phenol) is fitted satisfactorily with only one additional parameter per compound, which is shown to be a strong function of the reduced dipole moment. Two parameters are needed for hydrogen bonding compounds (alcohols, water), but for alcohols, one parameter has been kept constant and the other expressed as a function of the reduced dipole moment. The extension of the correlation to mixtures is satisfactory, direct, and involves only one coefficient per binary.

Orbital energy control of cycloaddition reactivity

Abstract: A reactivity model for concerted cycloaddition reactions is presented which allows a systematization of substituent effects. The treatment is based on the frontier electron theory of Fukui. The consideration of the energy separations of HOMOs (Highest Occupied Molecular Orbitals) and LUMOs (Lowest Unoccupied Molecular Orbitals) leads to three reactivity types in these cycloadditions. For the Diels–Alder addition and 1, 3-dipolar cycloadditions the occurrence of: 1. HOMO (Diene or Dipole)–LUMO (olefin) controlled reactions, 2. HOMO (Diene or Dipole)–LUMO (olefin) and HOMO (olefin)–LUMO (Diene or Dipole) controlled additions and 3. LUMO (Diene or Dipole)–HOMO (olefin) controlled cycloadditions is demonstrated. Each type exhibits a characteristic behaviour towards substituents in both reaction partners. A semiquantitative treatment of substituent effects together with an experimental verification is given.

Surface dipole moments of close-packed un-ionized monolayers at the air-water interface

Abstract: Surface potentials (ΔV) of insoluble monolayers spread at the air-water interface have usually been interpreted in terms of the equation ΔV = 4Πnμ⊥. Here n is the number of film molecules/cm2 and μ⊥ is defined as the surface dipole moment. It may be assumed that μ⊥ is a composite quantity and that μ ⊥ = μ 1 D 1 + μ 2 D 2 + μ 3 D 3 Here μ1, μ2 and μ3 are the contributions to μ⊥ from substrate molecules, spread film terminal (in the water) dipoles and spread film terminal (out of the water) dipoles, respectively, and D1, D2 and D3 are local effective dielectric constants. This paper shows how all these quantities may be estimated from bulk dipole moment data and experimental measurements of surface potentials. The calculated quantities are then used to predict the surface conformations of other insoluble monolayer films and to explain observed differences in surface potentials for aliphatic and aromatic film forming molecules with similar terminal polar groups.

Generalized mean spherical approximations for polar and ionic fluids

Abstract: Generalized mean spherical approximations are solved for polar and ionic fluids. They are generalizations of previous mean spherical results in the sense that more general forms for the direct correlation function c(12) are considered than heretofore. In the case of a polar fluid, c(12) outside a hard‐sphere core is taken to be a sum of an ideal dipole term, a Yukawa term, and two short‐ranged terms, one of which is a shielded dipolar interaction, the other of which is a shielded ``classical Heisenberg'' interaction. In the ionic case, c(12) outside the core is taken to be the sum of Coulomb and Yukawa terms. In both cases, the coefficients of all terms can be independently adjusted. Two applications of our generalized mean spherical results are discussed. The first generates improved approximations with built‐in thermodynamic consistency. The second is a more straightforward use of the generalization to provide mean spherical approximations for a wider class of potentials.

PNO-CI and CEPA studies of electron correlation effects

Abstract: Ab initio calculations of the potential curves of low laying electronic states of OH are performed on the basis of a variational configuration interaction wavefunction (PNO-CI) and the coupled electron pair approximation (CEPA). The latter approach yields a ground state potential curve which deviates from the RKR curve by less than 200 cm−1 in the region from 0.7 to 1.6 A. Calculated ground state constants are as follows (experimental values in parentheses): r e = 0.972 (0.971) A, B e = 18.85 (18.87) cm−1, α e = 0.727 (0.714) cm−1, ω e = 3742 (3739) cm−1, ω e χ e = 85.3 (86.4) cm−1, μ0 = 1.686 (1.66) D, D e = 4.35 (4.63) eV,IP = 12.78 (13.36?) eV, El.Aff. = 1.51 (1.83) eV, v 00(2Π↔2Σ+) = 32690(32440) cm−1. The correlation contributions to ionization, excitation and electron attachment are analyzed. On the basis of estimated CEPA-limits, which are in very good agreement with experiment for D e and electron affinity, an IP of 13.0eV is recommended. Dipole moment expectation values and some IR transition probabilities are calculated from the ground state dipole moment curves. The calculated crossing point of the 2Σ− curve with the repulsive 4Σ− state is not in agreement with the position deduced from intensity data.

Solution of a model for the solvent‐electrolyte interactions in the mean spherical approximation

Abstract: An electrolytic solution is simulated by a mixture of charged hard spheres and hard dipoles, all of the same size. This model can be solved exactly in the mean spherical approximation (MSA), yielding a set of three coupled high order algebraic equations for three unknowns, which are essentially the excess internal energies due to the charges alone, the dipoles alone, and the charge‐dipole cross interaction. A rapidly converging series solution of these equations is proposed for the dilute solution regime. The first term in this series is the hard‐core Debye‐Huckel theory term, with electrostrictive corrections. We also obtain the leading term in the expansion for the infinite dilution limit of the ion‐solvent excess chemical potential. Other relevant information could be obtained using standard formulas.

Perturbation theories for polar fluids

Abstract: The free energy of dense fluids with permanent dipoles is computed through the Monte Carlo method with two types of intermolecular interaction: Stockmayer potential and hard-sphere potential with an added dipolar interaction. A comparison is made with the Pade representation recently proposed by Stell which is shown to be good. In the case of hard spheres with permanent dipoles we propose another equally successful perturbation theory, which is based on a partial resummation of the mixed perturbation theory first introduced by Lebowitz, Stell, and Baer. This perturbation theory is then applied to the general case of an interaction composed of a spherically symmetric two-body potential with permanent dipoles.

Exact solution of the mean spherical model for strong electrolytes in polar solvents

Abstract: The mean spherical model (MSM) for dense fluids is solved for an arbitrary mixture of equal radii charged hard spheres with permanent embedded dipole moments. The model provides a treatment of ionic solutions that includes the feature of a molecular solvent. Thus, it gives a basis for investigating deviations from the familiar continuum dielectric model in ionic solution theory. The arbitrary polar‐ionic mixture is first reduced to an effective two component problem. One component is an effective charged species while the other is an effective polar species. This two component problem is solved in terms of three parameters closely related to the thermodynamic functions of the fluid. Nonlinear algebraic equations for these parameters are obtained. Although these equations appear to be analytically intractable for arbitrary ionic and dipolar strengths, explicit results are obtained for low ionic strength. In this limit, the ion‐ion contribution to the Helmholtz free energy is given by the classical Debye‐Hu...

Magnetic field of Jupiter and its interaction with the solar wind

Abstract: Jupiter's magnetic field and its interaction with the magnetized solar wind were observed with the Pioneer 10 vector helium magnetometer. The magnetic dipole is directed opposite to that of the earth with a moment of 4.0 gauss R_J^3 (R_J, Jupiter radius), and an inclination of 15° lying in a system III meridian of 230°. The dipole is offset about 0.1 R_J north of the equatorial plane and about 0.2 R_J toward longitude 170°. There is severe stretching of the planetary field parallel to the equator throughout the outer magnetosphere, accompanied by a systematic departure from meridian planes. The field configuration implies substantial plasma effects inside the magnetosphere, such as thermal pressure, centrifugal forces, and differential rotation. As at the earth, the outer boundary is thin, nor diffuse, and there is a detached bow shock.

Spectroscopy and collision theory. III. Atomic eigenchannel calculation by a Hartree-Fock-Roothaan method

Abstract: Previous papers have expressed various experimental spectral data in terms of a single set of parameters (eigen-quantum-defects, transformation matrix, and excitation dipole moments). The parameters pertain to eigenstates of an electron-ion scattering matrix which represents only the effect of short-range interactions. This paper presents a method for calculating the same parameters by solving the many-electron Schr\"odinger equation for an atom within a limited spherical volume. Quantitative results, for Ar states with $J=1$ and odd parity, are compared with data extracted earlier from an analysis of spectral data, and are also used to reproduce the first 65 discrete line positions and their intensities, the positions and profiles of autoionization lines, and the branching ratio of the photoionization.

H3+: Geometry dependence of electronic properties

Abstract: As the first step to the ab initio calculation of the vibration‐rotation spectrum of the H3+ ion, we present results of configuration‐interaction calculations of the potential‐energy surface and the geometry‐dependent electric dipole and quadrupole moments for the ground electronic state. Interpolation on the potential‐energy surface, required for setting up the Hamiltonian matrix for nuclear motion, is facilitated by use of generalized Morse functions and Fourier analysis. An analysis of the equilibrium geometry and harmonic force constants is based upon the present and previous calculations. We conclude that H3+ has its potential minimum in an equilateral geometry with bond distances of 1.65 a.u. and harmonic frequencies ωA=3471 cm−1 and ωE=2814 cm−1.

Molecular dipole electrets

Abstract: The total polarization due to molecular dipoles in a glassy electret is computed using an Onsager cavity approach. From this result, all the possible contributions to the piezoelectric and pyroelectric coefficients are considered. It is shown that there are major contributions from the variation in dielectric constant and, for pyroelectricity, from thermal motion. These results account well for experimental data for polyvinyl chloride.

Model for the effects of a condensed phase on the infrared spectra of hydrogen-bonded systems

Abstract: A formal scheme is developed for treating the effects of a condensed phase on the vibrational spectrum of hydrogen‐bonded systems. A coupling of the moving proton to the bath is assumed responsible for the broadening, and is taken as simply the electrostatic interaction between the protonic dipole and the random local field set up by the internal modes of the bath or solvent. This corresponds to the electrostatic broadening. A strong‐coupling treatment is employed. The spectrum is found by a cumulant expansion of the dipole‐dipole correlation function. Expressions for the shift and broadening of the individual lines are given. The dynamics, as well as the strength, of the system‐bath coupling are important for determining lineshape. The lineshape is thus related to the microscopic dynamic behavior of the hydrogen‐bonded system in solution.

Macroscopic electromagnetic theory of resonant dielectrics

Abstract: The application of the macroscopic Maxwell equations to the resonant interaction of electromagnetic radiation and dielectric crystals consisting of molecules coupled via retarded dipole fields is investigated. The macroscopic fields are defined by space averaging over volume elements of linear dimensions $\ensuremath{\Delta}$ satisfying $a\ensuremath{\ll}\ensuremath{\Delta}\ensuremath{\ll}\ensuremath{\lambda}$, where $a$ is the intermolecular separation and $\ensuremath{\lambda}$ the wavelength in vacuo. The essential point of our method is the direct derivation from the microscopic equations of a constitutive relation for a finite dielectric, taking proper account of the radiation reaction terms and avoiding the use of an expansion in powers of the molecular polarizability. The results lead to a simple interpretation of the expressions for the internal fields derived by Vlieger along similar lines, and verify the validity of the standard equations of dispersion theory to all points inside the medium a distance $\ensuremath{\Delta}$ away from the surface. The transmission and scattering of radiation at or near a molecular resonance by media of over-all extent small and large compared to the wavelength are discussed for sphere and slab geometries, and the effective natural linewidths are calculated. The limits of validity of the constitutive relation are discussed, and the existence of frequency regions where the macroscopic description breaks down due to the appearance of large spatial variations in the dipole moments is pointed out. As an example of such "antiresonant" behavior and of the role played by the higher-order radiation-damping terms, the scattering of light from two interacting molecules is treated in detail. In the absence of sufficiently strong dissipative damping, the occurrence of antiresonance is predicted to be a general phenomenon giving rise to large oscillations in the scattering cross section even in the presence of spatial dispersion in a narrow region around the frequency where the expression for the macroscopic index of refraction diverges.

Wireless subterranean signaling method

Abstract: A relatively low frequency wireless electromagnetic communication link is established through a subterranean lossy medium such as ground or water by launching and propagating magnetic waves of generally vertical magnetic polarization through the intervening subterranean region of earth or water between a pair of magnetic dipole antennas. A suitable subterranean dipole magnetic antenna includes an elongated electrical solenoid having a ferromagnetic core, as of ferrite or laminated iron. Relatively low frequency magnetic waves are utilized wherein the frequency is related to the conductivity of the subterranean region and distance between transmitter and receiver such that the range is less than 10 skin depths at the carrier frequency.

Multiconfiguration self-consistent-field calculation of the dipole moment function of CO/X 1 sigma +/

Abstract: Using the optimized valence configurations (OVC) multiconfiguration self-consistent-field (MCSCF) method, the dipole moment function for the ground state of CO in the vicinity of the equilibrium internuclear distance has been calculated. The OVC MCSCF calculation results are compared with existing Hartree-Fock and configuration interaction treatments of this molecule at single points and also the dipole moment function deduced from experimental infrared intensities. A general prescription for constructing OVC wavefunctions for diatomic molecules is also presented.

The protons and electrons trapped in the Jovian dipole magnetic field region and their interaction with Io

Abstract: Detailed analysis of electrons equal to or greater than 3 MeV and of protons 0.5 to 1.8 MeV and equal to or greater than 35 MeV for both the inbound and the outbound passes of the Pioneer 10 spacecraft. Conclusive evidence is obtained that the trapped radiation in Jupiter's inner magnetosphere is maintained and supplied by inward diffusion from the outer regions of the trapped radiation zone. It is shown that the time required for isotropization of an anisotropic flux by pitch angle scattering inside L approximately equal to 6 is long in comparison with the time required for particles to diffuse inward from L approximately equal to 6 to L approximately equal to 3, that the high-energy protons were not injected at high energies by the Crand (cosmic ray albedo neutron decay) process but were accelerated in the magnetosphere of Jupiter, and that the main conclusions of this analysis are unaffected by use of either the D sub 1 or the D sub 2 magnetic field models. Theoretical studies of the capture of trapped electrons and protons by Io have been carried out, and it is found that the probability of capture by Io depends strongly upon the particle species and kinetic energy.

Determination of the structure of ArHF

Abstract: Radio‐frequency and microwave spectra of K = 0 states of ArHF in the ground vibrational state have been measured by molecular beam electric resonance spectroscopy. The rotational constant is (B+C)/2=3065.719 MHz; the component of the dipole moment along the a inertial axis is μa = 1.332 D. From the centrifugal distortion constant, DJ = 72.1 kHz, the stretching frequency of the van der Waals bond is estimated to be 42.1 cm−1. In analogy with ArHCl the internal Ar–F–H angle θ is expected to be acute and the average value of the angle is 48.20°. The equilibrium configuration is likely to be near linear with atomic arrangement ArHF. The vibrationally averaged Ar–F distance is 3.540 A.