Showing papers on "Dipole published in 1973"
TL;DR: The equilibrium dipole moment of the water molecule has been determined from Stark effect measurements on two H2O, one D2O and six HDO rotational transitions as discussed by the authors.
Abstract: The equilibrium dipole moment of the water molecule has been determined from Stark effect measurements on two H2O, one D2O, and six HDO rotational transitions. The variation of the dipole moment projection operator with rotational state is taken into account and expressions are given for this operator evaluated in the ground vibrational states of the three isotopes. The value obtained for the equilibrium dipole moment is |0μx| = 1.8473 ± 0.0010 D. The effective dipole moments in the principal axis energy representation are |μb (HOH)| = 1.8546 ± 0.0006 D, |μb (DOD)| = 1.8558 ± 0.0021 D and |μb (DOH)| = 1.7318 ± 0.0009 D, |μa (DOH)| = 0.6567 ± 0.0004 D.
627 citations
TL;DR: In this paper, the average-dipole-orientation theory has been parameterized to permit determination of capture limit rate constants by reading a graph and making a simple calculation, and a graph covering the range of polarizabilities and dipole moments of most molecules is included.
431 citations
TL;DR: In this article, an ion-permanent dipole interaction theory was developed that takes into consideration the thermal rotational energy of the polar molecule. But the theory is formulated in terms of an r-dependent average orientation angle θ (r) between the dipole and the line of centers of collision.
Abstract: A classical theory for the ion‐permanent dipole interaction is developed that takes into consideration the thermal rotational energy of the polar molecule. The theory is formulated in terms of an r‐dependent average orientation angle θ (r) between the dipole and the line of centers of collision. The technique allows quantitative determination of the capture cross section as a function of ion‐polar molecule relative velocity. In addition, capture limit rate constants are readily calculated both at thermal energies and as a function of relative energy. Charge transfer rate constants from various rare gas ions to difluorobenzene and dichloroethylene isomers have been measured at thermal energies using ion cyclotron resonance spectroscopy. Rate constants are considerably larger than predicted by the capture theories for both polar and nonpolar isomers indicating long range electron jump is a prevalent mechanism for charge transfer in these systems. The average‐dipole‐orientation theory developed in this pape...
383 citations
TL;DR: In this paper, structural and electronic models are proposed which correlate Goldstein's LEED, Auger, photo-emission, plasmon, and desorption data for negative electron affinity (NEA) on Si(100) surfaces.
286 citations
TL;DR: Optical absorption and emission intensities for trivalent rare earths in YAl${\mathrm{O}}_{3} were investigated in this article, where the Judd-Ofelt approach and phenomenological parameters for each ion were used to derive the electric dipole intensities.
Abstract: Optical absorption and emission intensities are investigated for trivalent rare earths in YAl${\mathrm{O}}_{3}$. Ions examined included Pr, Nd, Eu, Tb, Ho, Er, Tm, and Yb. Oscillation strengths of $f\ensuremath{\rightarrow}f$ transitions between $J$ manifolds were measured at room temperature and compared with calculated electric and magnetic dipole oscillator strengths. The Judd-Ofelt approach and phenomenological parameters for each ion were used to derive the electric dipole intensities. The intensity parameters, which were obtained for a least-square-fitting procedure, exhibited a general decrease with increasing number of $4f$ electrons throughout most of the series. The intensities for Pr and Tb were not satisfactorily accounted for in the present theory; some reasons for this are presented.
264 citations
TL;DR: In this paper, an argon discharge source is used to estimate the underlying continuum absorption in the banded region of I2 in the region 4200-8000 A. The A[1u(3Π)]← X absorption is found to be a factor of 2 stronger than previous estimates with a peak extinction of 41 liter mole−1 · cm−1 at 6730 A.
Abstract: New extinction coefficient measurements are reported for I2 in the region 4200–8000 A. An argon discharge source is used to estimate the underlying continuum absorption in the banded region. Together with other work these results locate the maximum in the 1 u(1Π) ← X[O+g(1Σ)] absorption at 4985 A with a peak extinction of 200 liter mole−1 · cm−1. From the shape of the spectrum the 1u (1Π) potential curve behaves as r−9 in the region of strong absorption. The A[1u(3Π)]← X absorption is found to be a factor of 2 stronger than previous estimates with a peak extinction of 41 liter mole−1 · cm−1 at 6730 A. Earlier indications of a linear dependence of the dipole strength on r centroid for the B [O+u(3Π)]↔ X system are supported in this study. Spectroscopic data for the B↔ X transition are reviewed and new spectroscopic constants recommended for the B state.
245 citations
TL;DR: A general expression is developed for the quasi-static magnetic field outside an inhomogeneous nonmagnetic volume conductor containing internal electromotive forces and it is shown that the external magnetic field vanishes under conditions of axial symmetry.
219 citations
TL;DR: The qualitative properties of an open magnetosphere and its electric field are examined and compared to a simple model of a dipole in a constant field and to actual observations as mentioned in this paper, showing that the electric field in the central polar cap tends to point from dawn to dusk for a wide choice of external fields.
Abstract: The qualitative properties of an open magnetosphere and its electric field are examined and compared to a simple model of a dipole in a constant field and to actual observations. Many of these properties are found to depend on the separatrix, a curve connecting neutral points and separating different field-line regimes. In the simple model, the electric field in the central polar cap tends to point from dawn to dusk for a wide choice of external fields. Near the boundary of the polar cap electric equipotentials curve and become crescent-shaped, which may explain the correlation of polar magnetic variations with the azimuthal component of the interplanetary magnetic field, reported by Svalgaard. Modifications expected to occur in the actual magnetosphere are also investigated: in particular, it appears that bending of equipotentials may be reduced by cross-field flow during the merging of field lines and that open field lines connected to the polar caps emerge from a long and narrow slot extending along the tail.
216 citations
TL;DR: In this paper, the dipole moment function of Clough, Beers, Klein, and Rothman was used to obtain rotationless moments of 1.8546 ± 0.0004 D for H2O and 1.85045 ± 0 4 D for D2O.
Abstract: Molecular beam electric resonance spectroscopy has been used to make precision Stark effect measurements on the 111, 110, and 211 rotational states of H2O and the 111, 110, 211, and 313 states of D2O. These data have been analyzed using the dipole moment function of Clough, Beers, Klein, and Rothman [J. Chem. Phys. 59, 2254 (1973)] to obtain rotationless moments of 1.8546 ± 0.0004 D for H2O and 1.8545 ± 0.0004 D and D2O.
213 citations
TL;DR: In this article, a model based on tight-binding combinations of bonding hybrid orbitals is explored, which attempts to relate a wide range of properties to a few parameters of covalent and polar solids.
Abstract: A model electronic structure is explored which attempts to relate a wide range of properties to a few parameters of covalent and polar solids. The model is based upon tight-binding combinations of bonding hybrid orbitals. Of the many overlap matrix elements which enter, only three are retained; the three are associated with covalency, polarity, and metallicity. Many properties may be computed quite simply in terms of the parameters of the model, and measured values of the properties can then be used to determine the parameters. In this study the matrix elements associated with metallicity are obtained directly from the atomic-term values; those associated with covalency and polarity are obtained from the static dielectric constant using essentially the approach of Phillips, but in terms of the formula for the dielectric constant appropriate to this model. Also calculated in terms of the model were the valence energy bands themselves, obtained explicitly for silicon and for gallium arsenide. In treating other properties the unitarity of the final diagonalization was utilized to avoid carrying it out explicitly. The dipole moment of the individual bonds was defined and calculated as was an effective ionic charge and the macroscopic transverse charge. The cohesive energy was also obtained for ionic and metallic structures as well as for the covalent tetrahedral structures. Criteria for the stability of each structure were thereby obtained. The model also explains why some properties scale approximately linearly with the ionicity defined by Phillips.
197 citations
TL;DR: In this article, the decay function of the electric dipole polarization has been calculated in terms of the correlation function of Wigner rotation matrices, and the orientational potential energy function has been expanded as a series of Legendre polynomials.
Abstract: The dipole relaxation behaviour in liquid crystals as a function of the molecular ordering has been interpreted theoretically. The decay function of the electric dipole polarization has been calculated in terms of the correlation function of the Wigner rotation matrices. The orientational potential energy function has been expanded as a series of Legendre polynomials, and the contributions of the various terms investigated.
TL;DR: In this paper, the authors measured diffusion coefficients for n-paraffins ranging in size from ethane to n-tetradecane in potassium T zeolite.
TL;DR: The renormalization of the axial coupling constant in nuclei is related by PCAC to the exchange effects in the pionic vertex as mentioned in this paper, and the analogy between this problem and that of an electric dipole inside a dielectric medium is pointed out.
TL;DR: In this paper, the solvent shift effect is caused by a weak interaction between the solute and surrounding solvent molecules and is best treated using quantum-mechanical perturbation theory that allows it to be divided into electrostatic type interactions and dispersion interactions.
Abstract: Publisher Summary The spectrum of a substance in a solution is changed compared to its spectrum in the vapor state. Solvent-shift effect is caused by a weak interaction between the solute and surrounding solvent molecules. The change in energy of the system because of this interaction will differ depending on if the solute molecule is in its ground or excited state and consequently there will be the change in excitation energy observed experimentally. The solvent–solute interaction, being weak, is best treated using quantum–mechanical perturbation theory that allows it to be divided into electrostatic type interactions and dispersion interactions. The electrostatic type interactions relate the solvent shift to the change in dipole moment and polarizability of the solute molecule on excitation from its ground state to its excited state and thus, can give experimental values-albeit once removed-of excited-state dipole moments and polarizabilities. The order-of-magnitude values for excited-state dipole moments can be obtained from solvent shift data. All solvent-shift theories are based on the assumption that solvent and solute molecules are sufficiently well separated that overlap of electronic distribution can be neglected. The chapter proves with the help of calculations that Abe's theory and the reaction-field method differ by very little in the final analysis. The solvent-shift data can also be used to obtain the order of magnitude estimates of excited-state dipole moments.
TL;DR: In this article, a phenomenological dielectric approximation is proposed for studying the response of metal surfaces to external charge distributions and is illustrated by detailed calculations using the Thomas-Fermi model.
Abstract: A phenomenological dielectric approximation is proposed for studying the response of metal surfaces to external charge distributions and is illustrated by detailed calculations using the Thomas-Fermi model. The procedure is based on the replacement of the dielectric-response kernel in a constitutive relation by its asymptotic expression in the bulk region. It represents an alternative to the classical step-density approximation, where the nonuniform density profile near the surface is replaced by the bulk electron density up to an abrupt termination. While the two procedures are equivalent for a local solid, they are quite different in general because of the different nature of the quantitites being approximated by bulk expressions. Detailed applications include the calculation of the image-potential interaction and of the induced surface dipole for static point charges external to the metal surface, the study of the corresponding quantities for charges embedded in the surface, and, finally, the calculation of the effective polarizability of an adsorbed atom and of the image potential and induced surface dipole for a polarizable ion. Comparison with self-consistent surface-model calculations indicates that for charges external to the surface the results for the above-mentioned dielectric approximation are much more realistic than those for the step-density approximation. However, for the case of embedded charges far away from the surface the step-density approximation yields a more accurate result for the surface dipole. A final section is devoted to the generalization of the step-density treatment to time-dependent response problems, assuming specular reflection of electrons at the surface. Some necessary general formulas are derived in a first part, which is then followed by a detailed study of the image-potential interaction for point charges moving uniformly along various prescribed trajectories. Explicit calculations for a local dielectric function indicate a strong dependence of the instantaneous interaction on the past trajectory of the external charge, as well as strong deviations from the quasistatic image potential in some cases. These modifications arise from real and virtual excitation of surface plasmons for particles moving outside the metal, and from both surface- and bulk-plasmon excitation for particles moving inside the metal.
TL;DR: In this article, the theoretical wave nature of the electromagnetic fields about various types of dipole sources placed on the surface of a low-loss dielectric half-space and two-layer earth was examined.
Abstract: Radio interferometry is a technique for measuring in‐situ electrical properties and for detecting subsurface changes in electrical properties of geologic regions with very low electrical conductivity. Ice‐covered terrestrial regions and the lunar surface are typical environments where this method can be applied. The field strengths about a transmitting antenna placed on the surface of such an environment exhibit interference maxima and minima which are characteristic of the subsurface electrical properties. This paper (Part I) examines the theoretical wave nature of the electromagnetic fields about various types of dipole sources placed on the surface of a low‐loss dielectric half‐space and two‐layer earth. Approximate expressions for the fields have been found using both normal mode analysis and the saddle‐point method of integration. The solutions yield a number of important results for the radio interferometry depth‐sounding method. The half‐space solutions show that the interface modifies the directio...
TL;DR: A new formulation is presented for surface potentials produced on a homogeneous spherical volume conductor by an eccentric current dipole contained therein, free of interminancies for all relevant dipole locations and leads directly to the solution ofsurface potentials due to an eccentric quadripole.
Abstract: A new formulation is presented for surface potentials produced on a homogeneous spherical volume conductor by an eccentric current dipole contained therein. The formulation is free of interminancies for all relevant dipole locations and leads directly to the solution of surface potentials due to an eccentric quadripole.
TL;DR: Onsager's theory of dipole moments is modified for radially inhomogeneous permittivity [form ϵ( r )=ϵ B exp(κ/ r )] arising at the cavit as mentioned in this paper.
TL;DR: In this article, the influence of the coupling of the proton movement and the H bond stretching vibration in a double minimum potential energy surface on the energy levels, transitions, induced dipole moments and polarisabilities is calcualted ab initio as a function of an electric field for the H5O+2 system.
Abstract: The influence of the coupling of the proton movement and the H bond stretching vibration in a double minimum potential energy surface on the energy levels, transitions, induced dipole moments and polarisabilities is calcualted ab initio as a function of an electric field for the H5O+2 system. The high polarisability of the hydrogen bonds remains to a large extent unchanged due to the coupling. New types of transitions occur, particularly when the tunnelling frequency and the frequency of the bond stretching vibration are comparable in size. Especially in this case numerous Fermi resonances occur due to the shift of the energy levels in the electric field, which leads to a considerable increase in the number of transitions. It is shown that the change of the frequencies of the transitions due to the induced dipole interaction of the bonds with fields from their environment is a decisive cause of the variety of energy level differences observed as a continuous absorption in the i.r. spectrum of such systems.
TL;DR: The CO stretching frequency of liquid ethylene and propylene carbonates is higher in the infrared than in the Raman spectrum as mentioned in this paper, which is explained by a coupling between the transition dipoles of neighbouring molecules, made possible by some degree of alignment of molecular dipoles due to the high dipole moment of these molecules.
Abstract: The CO stretching frequency of liquid ethylene and propylene carbonates is higher in the infrared than in the Raman spectrum. The difference amounts to 13 cm–1 for ethylene carbonate at 313 K. This effect is explained as the consequence of a coupling between the transition dipoles of neighbouring molecules, which is made possible by some degree of alignment of molecular dipoles due to the high dipole moment of these molecules (about 16 × 10–30 C m). A study of dilution and temperature effects confirms this interpretation.
TL;DR: In this paper, a first-order perturbation treatment of S(q) is presented, using as a reference a system of molecules with isotropic forces, and the theory is used to predict the effect on Sq of anisotropic dispersion, overlap and multipole (dipole, quadrupole, octopole, and hexadecapole) forces for linear AA, AB and BAB molecules, and also for tetrahedral AB4 molecules and octahedral AB6 molecules.
Abstract: The structure factor S(q) for a fluid of rigid molecules is related to the angular pair correlation function, g(R 12ω1ω2). Several limiting cases of this relation are considered, and its use as a means of obtaining experimental knowledge of orientation correlations is briefly discussed. A first-order perturbation treatment of S(q) is presented, using as a reference a system of molecules with isotropic forces. The theory is used to predict the effect on S(q) of anisotropic dispersion, overlap and multipole (dipole, quadrupole, octopole, and hexadecapole) forces for linear AA, AB and BAB molecules, and also for tetrahedral AB4 molecules and octahedral AB6 molecules. Comparison with experiment is made for liquid bromine and liquid carbon tetrachloride; for both liquids orientation correlations make a substantial contribution to S(q). The theoretical calculations suggest that the most important anisotropic force contribution to S(q) is probably the quadrupolar force in the case of bromine, and the octopolar f...
TL;DR: In this paper, an equation was derived expressing optical rotation in terms of a set of relay tensors, which describe the manner in which the external field acting at one unit of a molecule induces a dipole moment in another unit.
Abstract: An equation is derived expressing optical rotation in terms of a set of ``relay tensors,'' which describe the manner in which the external field acting at one unit of a molecule induces a dipole moment in another unit. These tensors can be calculated from the polarizabilities of the units and the geometry of the molecule using either an exact treatment of point dipole interactions or perturbation approximations of any order. The derivation corrects certain previous errors in the calculation of induced electric and magnetic moments. The equation is transformed into alternative forms expressing the rotation in terms of electric and magnetic moments associated with certain sets of molecular normal modes in a manner analogous to Rosenfeld's quantum mechanical equation. One form gives an analytical expression for rotatory dispersion in terms of the polarizability dispersion parameters for individual units. Calculated rotations are given for a simple hypothetical molecule and for CHFClBr, in both cases showing ...
TL;DR: In this paper, the first singlet excited state of biphenyl was assigned as 1B3g (33128.2 cm−1 (h10, 33270.4 cm −1 (d10) and transitions to it are consistent with a magnetic dipole mechanism by polarization measurements and calculations.
Abstract: The absorption and fluorescence spectra of biphenyl‐h10 and biphenyl‐d10 neat crystals, and of lightly and heavily doped isotopically mixed crystals have been studied at 4.2 °K. The first singlet excited state of biphenyl is assigned as 1B3g (33128.2 cm−1 in biphenyl‐h10, 33270.4 cm−1 in biphenyl‐d10) and transitions to it are found to be consistent with a magnetic dipole mechanism by polarization measurements and calculations. The bulk of the intensity in the 1B3g ⇄1Ag(X) transitions is electric dipole arising from Herzberg‐Teller coupling through a mode b2u (9) at 626 cm−1 (h10) and ≈ 593 cm−1 (d10). The next excited state is assigned as 1B2u (M‐polarized) and the splitting of the 1B3g and 1B2u states of 746.8 ± 3 cm−1 provides the inter‐ring resonance interaction corresponding to the splitting of the 1B2u (D6h) state of benzene through excitation exchange interactions and second‐order shifts. The isotopic mixed crystal spectra provide evidence that the width of the biphenyl crystal exciton band (from 1...
TL;DR: The results establish the presence of a pair of copper ions at the active site of tyrosinase, and a clsoe structural relationship between this active site and that of hemocyanin.
Abstract: The Tr and T[unk] states of tyrosinase were treated with NO. EPR spectra of the products observed at 14°K and at 113°K showed mixtures of two signals. One had components in the region of g = 2, about 1200 G wide, and in the region of g = 4, showing hyperfine splitting. The other signal was similar to that arising from isolated Cu(II) ions in an axially symmetric environment. The first signal was indicative of Δm = 1 and Δm = 2 transitions arising from magnetic dipole-dipole coupled Cu(II) ion pairs. It closely resembled previously reported EPR spectra obtained from NO-treated hemocyanin, which were confirmed in this study. The normal Curie behavior of the signals between 230°K and 14°K ruled out significant exchange coupling between the ion pairs. The Δm = 2 signals were not saturable up to 350 mW at 14°K. The broad Δm = 1 signals could be separated from accompanying signals by the saturation characteristics of the latter at about 10 mW at 14°K. The results establish the presence of a pair of copper ions at the active site of tyrosinase, and a clsoe structural relationship between this active site and that of hemocyanin.
TL;DR: The shape of the magnetosphere has been calculated self-consistently for inclinations of the earth's magnetic dipole from perpendicular to the solar wind as discussed by the authors, and the neutral point region has been given precise study in one degree steps and is found to have a smooth continuous curvature.
TL;DR: In this article, the authors presented numerical calculations of magnetic dipole moments, magnetic octupole moments and transition probabilities in odd-mass nuclei around 208 Pb. The calculations were performed in the framework of the theory of finite Fermi systems with an effective magnetic operator.
TL;DR: In this article, the authors treated the chemisorption of hydrogen on metals by a self-consistent calculation, where three dimensional charge densities, interaction energies and dipole moments were given as a function of position of the hydrogen adatoms.
Abstract: : The chemisorption of hydrogen on metals is treated by a self-consistent calculation. Three dimensional charge densities, interaction energies and dipole moments are given as a function of position of the hydrogen adatoms. The results are compared with experiment. The experimental picture of a dissociated adsorbate of small dipole moment is substantiated, and the calculations are consistent with the observation that hydrogen field desorbs together with the surface atoms of the substrate. (Author)
TL;DR: The results demonstrate the importance of including the second order Zeeman effect and in-plane anisotropy when evaluating NMR dipolar shifts in low-spin hemin systems.