Showing papers on "Quadrupole published in 1985"
TL;DR: In this paper, the influence of vibrational motion on bond lengths and quadrupole constants obtained from dipolar and quadrrupolar solid state line shapes is considered and explicit expressions for the effective coupling constants that can be conveniently evaluated using the results of a normal mode analysis are derived.
Abstract: The influence of vibrational motion on bond lengths and quadrupole constants obtained from dipolar and quadrupolar solid state line shapes is considered. It is shown that such motions average both the magnitude and the orientation of the intrinsic interaction tensor. Explicit expressions for the effective coupling constants that can be conveniently evaluated using the results of a normal mode analysis are derived. When the vibrationally averaged interaction tensor is axially symmetric, it is shown that the effect of vibrational motion on relaxation can be rigorously incorporated into an effective coupling constant which is formally identical to the one that determines the line shape. Illustrative calculations for several alkanes, in both the gas and solid phases, are presented. The relative contributions of stretching and bending vibrations and the effect of anharmonicity on the effective C–H bond lengths and deuterium quadrupole constants are examined. The influence of vibrational averaging on the magnitude of the dipolar coupling is shown to be essentially independent of the nature of the molecule and its environment and to be quite small (i.e., for C–H bonds, the coupling constant decreases by 3% and hence the effective bond length increases by 1%). Vibrational averaging of the orientation of the dipolar interaction vector, on the other hand, depends on the size of the molecule and its environment because of the predominant role played by low frequency bending and torsional modes. The implication of these results for the value of the effective internuclear distance that should be used for the interpretation of the dipolar relaxation experiments is considered.
205 citations
TL;DR: In this article, upper and lower bounds to van der Waals C6, C8, and C10 coefficients for hydrogen, noble gas, alkali, and alkaline earth atoms are determined by using Pade approximants to bound the dynamic multipole polarizabilities.
Abstract: New upper and lower bounds to the van der Waals C6, C8, and C10 coefficients for hydrogen, noble gas, alkali, and alkaline earth atoms are determined by using Pade approximants to bound the dynamic multipole polarizabilities. Also, the nonadditive, three‐body coefficients involving dipole, quadrupole, and octupole interactions are bounded.
199 citations
01 May 1985
TL;DR: In this paper, the translational and rotational velocities of a colloidal particle in an applied electric field (E∞) were derived for the general case of a zeta potential (ζ) which varies with position on the particle surface.
Abstract: The translational and rotational velocities of a colloidal particle in an applied electric field (E∞) are derived for the general case of a zeta potential (ζ) which varies with position on the particle surface. Analytical results which are correct to O(∇E∞) are presented. The particle is modeled as a rigid, nonconducting sphere of radius a, and the analysis assumes ϰa → ∞ where ϰ is the Debye screening parameter of the surrounding fluid. The electrophoretic mobility in a constant field depends on the quadrupole moment of ζ and is not just related to the area-averaged zeta potential through Smoluchowski's equation, as is commonly assumed. The dipole moment of ζ contributes to rotation in a constant field, tending to align the particle. Dielectrophoretic motion results from the dipole moment interacting with ∇E∞ for unpolarized charge distributions, and from induced dipole and quadrupole moments for particles whose surface charge is mobile.
164 citations
TL;DR: In this article, a method for the determination of large polarized GTO/CGTO basis sets for the calculation of molecular properties is presented and illustrated by very accurate SCF and CAS SCF calculations of the dipole and quadrupole moments of the LiH molecule.
132 citations
TL;DR: In this paper, the coherent evolution of nuclear spin observables in zero magnetic field with the full sensitivity of high field NMR was described and demonstrated for detecting the magnetic dipole and electric quadrupole interactions of disordered systems without the line broadening associated with random orientation with respect to the applied magnetic field.
Abstract: Methods are described and demonstrated for detecting the coherent evolution of nuclear spin observables in zero magnetic field with the full sensitivity of high field NMR. The principle motivation is to provide a means of obtaining solid state spectra of the magnetic dipole and electric quadrupole interactions of disordered systems without the line broadening associated with random orientation with respect to the applied magnetic field. Comparison is made to previous frequency domain and high field methods. A general density operator formalism is given for the experiments where the evolution period is initiated by a sudden switching to zero field and is terminated by a sudden restoration of the field. Analytical expressions for the signals are given for a variety of simple dipolar and quadrupolar systems and numerical simulations are reported for up to six coupled spin-1/2 nuclei. Experimental results are reported or reviewed for 1H, 2D, 7Li, 13C, and 27Al nuclei in a variety of polycrystalline materials. The effects of molecular motion and bodily sample rotation are described. Various extensions of the method are discussed, including demagnetized initial conditions and correlation by two-dimensional Fourier transformation of zero field spectra with themselves or with high field spectra.
126 citations
TL;DR: In this article, Hartree-Fock calculations for the ground states of the diatomic systems He2, Li2, Be2, HF, OH, N2, CO, BF, NO+ and CN− are presented.
Abstract: Fully numerical two-dimensional Hartree-Fock calculations are reported for the ground states of the diatomic systems He2, Li2, Be2, HF, OH-, N2, CO, BF, NO+ and CN-. total energies, electric multipole moments and electric field gradients are given. A close agreement with the seminumerical results by McCullough is obtained. High multipole moments, up to Q 10, are reported and compared to LCAO ones. The role of correlation in nuclear quadrupole coupling constants is discussed.
107 citations
TL;DR: In this article, the NH3 monomer symmetry axis was found to have a vibrationally averaged displacement of 23.1° from the N...O axis, and no evidence for transfer of a proton from water to the ammonia was observed.
Abstract: Microwave and radio frequency spectra for NH3⋅H2O and deuterated analogs have been observed by molecular beam electric resonance spectroscopy. Rotational constant, Stark effect, and nitrogen quadrupole coupling interaction data were obtained. This complex is found to have a linear, hydrogen bonded structure with water as the proton donor. The NH3 monomer symmetry axis was found to have a vibrationally averaged displacement of 23.1° from the N...O axis. No evidence for transfer of a proton from water to the ammonia was observed.
98 citations
TL;DR: In this paper, the authors present evidence that cooling the ions by collisions with atoms of a background gas light compared to the ions results in the condensation of the ions into a cloud of almost uniform density determined by space charge versus potential well forces.
Abstract: The largest systematic uncertainty in the performance of atomic frequency standards using a cloud of ions stored in an rf quadrupole trap is the second-order Doppler shift which depends on ion temperature and trapping parameters. This paper presents evidence that cooling the ions by collisions with atoms of a background gas light compared to the ions results in the condensation of the ions into a cloud of almost uniform density determined by space charge versus potential well forces. In this condition the second-order Doppler shift is simple to calculate and is found to depend only on readily measured characteristics of the ion cloud. This along with already observed good signal-to-noise ratio shows that the frequency standard we have constructed using the hyperfine splitting of singly ionized199Hg, with helium cooling can have an order of magnitude better performance in accuracy, stability, and reproducibility than presently available commercial cesium beam standards.
95 citations
01 May 1985
TL;DR: In this article, the temperature anisotropy that would be produced in the cosmic microwave background by an isotropic, stochastic ensemble of primordial gravitational waves having a flat initial spectrum was calculated.
Abstract: A calculation is made of the temperature anisotropy that would be produced in the cosmic microwave background by an isotropic, stochastic ensemble of primordial gravitational waves having a flat initial spectrum. On angular scales THETA > 2 the anisotropy autocorrelation function has practically the same multipole dependence as previously established for the case of flat-spectrum adiabatic perturbations, while on scales THETA < 1 the anisotropy becomes insignificant. Upper limits are placed on the gravitational-wave amplitude and on the expected quadrupole anisotropy.
95 citations
TL;DR: In this article, a simple classical model is proposed which relates the deuterium quadrupole coupling constant to the bond length with high accuracy, and a theoretical study of the HCOOH dimer gives some insight into the importance of different mechanisms which lower the quadrupoles coupling constant in the solid.
Abstract: Deuterium quadrupole coupling constants were obtained for 39 sites from ab initio SCF calculations. An accuracy comparable to the experimental one is reached with a moderately large basis set of very high local quality. Comparison with experiment shows that electron correlation does not contribute substantially to this property. The experimental values for DNCO and DFCO should be reexamined, the value for CD3Cl in the literature was not properly transformed to the bond axes system, and the experimental value for ND3 agrees with the calculated one, thus showing that a dynamical model is not necessary. Several empirical relations are presented, and a simple classical model is proposed which relates the deuterium quadrupole coupling constant to the bond length with high accuracy. A theoretical study of the HCOOH dimer gives some insight into the importance of different mechanisms which lower the quadrupole coupling constant in the solid.
94 citations
TL;DR: In this article, a hybrid mass spectrometer of BEQQ geometry (B, magnetic sector; E, electric sector; Q, quadrupole mass filter) is described.
TL;DR: The quadrupole shift for the central transition in magic-angle-spinning spectra of nuclei with non-integer spins in powder samples is smaller than the half-width of the line as discussed by the authors.
TL;DR: In this paper, the authors applied the derivative Hartree-fock (DHF) theory to calculate the electrical polarizabilities of hydrogen, nitrogen, and acetylene in order to provide a more complete description than previously available.
Abstract: The electrical polarizabilities of a molecule are of potential importance in the molecule’s response to an applied field or in the interaction with other proximate molecules. Derivative Hartree–Fock (DHF) theory, which is an open‐ended, uniform procedure for calculating properties corresponding to derivatives of the electronic energy, has been applied in obtaining electrical polarizabilities of hydrogen, nitrogen, and acetylene. In order to provide a more complete description than previously available, this has been carried through the third level of differentiation with respect to electric field and field gradient components, thereby yielding dipole and quadrupole hyperpolarizabilities. Extensive basis set tests performed on hydrogen reinforce the established need for extended sets with diffuse functions, and for balance in the flexibility of the s, p, d,...type functions on each center. DHF is well suited to the use of such large basis sets and in the case of acetylene, a basis of 100 functions was used to calculate its electrical properties.
TL;DR: In this article, the hyperfine structures and isotope shifts of 14 isotopes of Eu (Z=63) in the mass range 140≦A≦153, partly with isomeric states, have been measured in the atomic transitions at 4,594 A and 4,627 A, using the technique of collinear fast-beam laser spectroscopy at the ISOLDE facility at CERN.
Abstract: The hyperfine structures and isotope shifts of 14 isotopes of Eu (Z=63) in the mass range 140≦A≦153, partly with isomeric states, have been measured in the atomic transitions at 4,594 A and 4,627 A, using the technique of collinear fast-beam laser spectroscopy at the ISOLDE facility at CERN. The nuclear spins, the magnetic dipole and electric quadrupole moments, and the changes in the mean square charge radii have been evaluated. These nuclear parameters clearly reflect the effects of theN=82 neutron-shell closure in the single-proton hole states with respect to the semi-magic gadolinium (Z=64), and theN=88−90 shape transition.
01 May 1985-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this article, a superoperator formalism was used to yield closed form expressions for the Mossbauer line shape in the presence of magnetic dipole and electric quadrupole hyperfine interactions.
Abstract: A new method is presented for the calculation of Mossbauer line shapes of hyperfine split nuclei Instead of solving explicitly the hyperfine Hamiltonian for its eigenvalues and eigenvectors this method uses a superoperator formalism to yield closed form expressions for the Mossbauer line shape in the presence of magnetic dipole and electric quadrupole hyperfine interactions The advantage of this method over the conventional one lies in the fact that averages over hyperfine field orientations may be calculated analytically This is demonstrated for the case of 57Fe with randomly oriented electric field gradients in a uniform oriented magnetic field
TL;DR: In this article, a systematic study of CO molecules is carried out by using the funite-field many-body perturbation theory, and the dipole and quadrupole moment functions are calculated by the complete fourth-order MBPT schemes and the corresponding correlation corrections are analysed.
TL;DR: In this paper, the electric field gradients at the oxygen and hydrogen nuclei were calculated for water clusters ranging from dimer to pentamer in an attempt to reproduce the shift in 17O and 2H nuclear quadrupole coupling constants (qccs) that is observed on going from ice to vapor.
Abstract: Using ab initio SCF molecular orbital techniques, the electric field gradients (efg’s) at the oxygen and hydrogen nuclei were calculated for water clusters ranging from dimer to pentamer in an attempt to reproduce the shift in 17O and 2H nuclear quadrupole coupling constants (qcc’s) that is observed on going from ice to vapor. For 2H, where the qcc shift is due mostly to the change in O–H bond length, excellent agreement with the experimental vapor → ice shift was obtained. For 17O, the change in the qcc is found to be mainly electronic in origin, effectively due to the polarization of the charge associated with the oxygen atom, and approximately 75% of the observed qcc shift was reproduced. On the basis of the calculations, estimates of the 17O and 2H qcc’s in liquid water were made that are consistent with the values obtained from an analysis of the available NMR relaxation data, provided that librational motions are properly taken into account. We also present results of SCF calculations on water interacting with a Li+, Na+, or Cl− ion, indicating that the effect of a nearby ion on the 2H and 17O qcc’s is similar to that produced by H bonding.
TL;DR: In this article, the temperature dependence of deuterium relaxation rates for the methylene groups of perdeuterated n−nonadecane in a urea clathrate single crystal was measured using Jeener-Broekaert experiments.
Abstract: Measurements of the temperature dependence of deuterium relaxation rates for the methylene groups of perdeuterated n‐nonadecane in a urea clathrate single crystal are reported Individual spectral densities J1(ω0) and J2(2ω0) were determined using Jeener–Broekaert experiments, and data obtained at two orientations of the main crystal axis were fit to a motional model which combines unrestricted rotational diffusion about the alkane long axis with restricted wobbling of the methylene group planes Both motions are fast on the NMR time scale and both affect the observed, time averaged quadrupole coupling constant (e2qQ/h)eff=163 kHz However, quadrupole tensor components appearing in the relaxation Hamiltonian should not be averaged over that part of the motion which is in fact responsible for the relaxation, and by fitting the relaxation data together with the observed quadrupolar splitting to the motional model described above we obtain a value ≥ 185 kHz for the methylene quadrupole coupling constant Thi
01 Aug 1985-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this article, a recoil mass spectrometer has been designed to operate at small angles including 0° for use with the XTU tandem accelerator, where two 20° electric dipoles and one −40° magnetic dipole are combined in a mirror-symmetric configuration.
Abstract: A wide acceptance recoil mass spectrometer has been designed to operate at small angles including 0° for use with the XTU tandem accelerator. Two 20° electric dipoles (ϱ = 4 m, Eϱ = 12 MV) and one −40° magnetic dipole (ϱ = 1 m, Bϱ = 10 kG m) are combined in a mirror-symmetric configuration similar to a proven design developed at the University of Rochester. Spatial focusing without intermediate cross-overs is achieved using the magnetic dipole plus a magnetic quadrupole doublet lens at the entrance. Weak quadrupole focusing in the dispersion plane avoids large chromatic aberrations. Two magnetic sextupole lenses combined with magnet boundary curvature remove focal plane tilt and minimize other second-order aberrations. Specifications are: solid angle acceptance >10 msr, energy acceptance ±20%, mass acceptance ±7%, mass dispersion 10 mm/% and mass resolution 1/280 at 5 msr and ΔE/E = ± 10%.
TL;DR: In this paper, the collision-induced absorption spectrum for nitrogen has been measured in the spectral region below 360 cm−1 at 126, 149, 179, and 212 k. The measurements have been obtained using Fourier transform infrared (FTIR) techniques, a far infrared (FIR) laser system operating at 84.2 and 15.1 k.
Abstract: The collision-induced absorption (CIA) spectrum for nitrogen has been measured in the spectral region below 360 cm−1 at 126, 149, 179, and 212 K. The measurements have been obtained using Fourier transform infrared (FTIR) techniques, a far infrared (FIR) laser system operating at 84.2 and 15.1 cm−1, and microwave cavity techniques. The experimental line shapes have been compared with the theoretical predictions of Joslin, based on Mori theory, and of Joslin and Gray, based on information theory alone. The data have been used to determine the quadrupole moment employing various intermolecular potentials. One Lennard–Jones potential has resulted in a quadrupole moment of 1.51 B, the value that was used in generating the theoretical line shapes. These results, when combined with our forthcoming measurements on nitrogen mixed with methane and argon, may be helpful in determining the role of CIA in calculating the opacity of some planetary atmospheres.
TL;DR: In this paper, a procedure for the construction of the gravitational multipoles is proposed, and the full metric is given in the case of a mass possessing a quadrupole moment.
Abstract: A procedure is proposed for construction of the gravitational multipoles. The full metric is given in the case of a mass possessing a quadrupole moment.
TL;DR: The 17 O quadrupole-coupling tensor in a single crystal of benzophenone was completely determined using high-field NMR, with B 0 of 8.4 T.
TL;DR: In this paper, the quadrupole mass spectra show singly ionized clusters up to Hg 8 +, which is well below the critical size for Coulomb explosions, calculated as sphere and as chain-like models.
TL;DR: In this paper, the frequencies and relative intensities of rotation-vibration transitions of 127 I 2, 129 I 2 and 127 I 129 I near the HeNe laser emission wavelength of 640 nm have been calculated.
TL;DR: Theoretical studies of the lowest 1S, 1, 3P and 1,3D states of calcium and strontium are presented in this paper, where the excitation energies, dipole-allowed transition moments and the 1D-1S quadrupole moment are studied as a function of the one-particle and molecular orbital bases and level of correlation treatment.
Abstract: Theoretical studies of the lowest 1S, 1,3P and 1,3D states of calcium and strontium are presented. The excitation energies, dipole-allowed transition moments and the 1D-1S quadrupole moment are studied as a function of the one-particle and molecular orbital bases and level of correlation treatment. Including core-valence correlation significantly reduces the magnitude of the dipole and quadrupole transition moments, producing oscillator strengths that lie within the experimental error bars. On the basis of relativistic effective-core potential calculations, the authors find that, unlike barium, the strontium transition moments are not significantly changed when relativistic effects are included. Spin-forbidden transitions were assumed to occur entirely as a result of the breakdown of LS coupling. The magnitude of the singlet-triplet mixing was determined both by ab initio calculation and from the observed deviations from the Lande interval rule. The calculated 1D2 state lifetime for Ca is 3.1+or-0.3 ms, which is in reasonable agreement with the experimental value of 2.3+or-0.5 ms (with an absolute upper bound of 4 ms). The dominant decay mechanism is spin-forbidden dipole-allowed transitions, with only 12% arising from quadrupole transitions. Similarly for the 1D2 state of Sr, the authors compute a radiative lifetime of 0.49+or-0.04 ms with only 2% of the decay from quadrupole transitions.
TL;DR: It is observed, for the first time in highly ionized atoms, electric quadrupole transitions between the 3p and 2p levels of fluorinelike and neonlike Xe/sup 45 +/ and XE/sup 44 +/.
Abstract: We have observed, for the first time in highly ionized atoms, electric quadrupole transitions between the 3p and 2p levels of fluorinelike and neonlike Xe/sup 45 +/ and Xe/sup 44 +/. We have made precision measurements (lambda/..delta..lambda = 2 x 10/sup 4/) of the relative wavelengths of the allowed electric dipole (E1) transitions and the forbidden electric quadrupole (E2) transitions connecting the n = 3 and the n = 2 levels. We have also derived from these measurements several ..delta..n = 0 intervals between states of opposite parity.
TL;DR: In this article, it was shown that CPT invariance alone requires the electromagnetic structure of a spin-J Majorana particle (J=half interger) to consist at most in toroid multipole moments and distributions with the multipolarity order L=1,2,...,2J; all other usual electric and magnetic multipole characteristics are forbidden.
Abstract: It is proven that CPT invariance alone requires the electromagnetic structure of a spin-J Majorana particle (J=half interger) to consist at most in toroid multipole moments and distributions with the multipolarity order L=1,2,...,2J; all other usual electric and magnetic multipole characteristics are forbidden. In the spin J=(3/2) case the covariant form of the electromagnetic vertex is obtained in terms of dipole, quadrupole, and octupole toroid form factors. It is suggested that under certain circumstances Majorana fermions with nonvanishing toroid multipole moments might give rise to Cherenkov or transition radiation.
TL;DR: In this paper, the effect of anomalous magnetic dipole and electric quadrupole moments of the charged weak boson on the muon anomaly was investigated and the constraints on those quantities derived from the experimental data were discussed.
TL;DR: In this paper, it was shown that the polarization of a polyatomic molecule is much more a transfer of charge along the molecular skeleton, an interatomic valence polarization, than a polarization of the charge cloud around each constituent atom and that what was essentially a singly polarized valence basis yields very many of the electrical properties in good agreement with extended basis set results.
TL;DR: In this paper, the hyperfine structure of the s, p and d states of the alkaline-earth ions have been evaluated using many-body theory and correlation effects were estimated by comparison with the isoelectronic alkali atoms.
Abstract: The hyperfine structure of the s, p and d states of the alkaline-earth ions have been evaluated using many-body theory. Polarisation effects were included to all orders and correlation effects were estimated by comparison with the isoelectronic alkali atoms. In addition to the magnetic dipole constant A for s, p and d states, the nuclear quadrupole moment for barium and the magnetic moment for some radium isotopes were estimated.