Showing papers on "Quadrupole published in 1991"
TL;DR: In this paper, a new cooling technique for heavy ions stored in a Penning trap was developed, where axial and cyclotron motions were cooled by buffer gas collisions, and the outward radial diffusion caused by the buffer gas was counteracted by an azimuthal quadrupole rf field.
496 citations
TL;DR: Oscillations with time-dependent period in the transmitted light intensity are quantitatively explained as resulting from quantum beats between the two branches of the exciton polariton.
Abstract: Coherent propagation of quadrupole polaritons in ${\mathrm{Cu}}_{2}$O is demonstrated by time-resolved spectroscopy. This manifests itself in a strong distortion of the temporal shape of a picosecond optical pulse which is in resonance with the 1S exciton polariton. Oscillations with time-dependent period in the transmitted light intensity are quantitatively explained as resulting from quantum beats between the two branches of the exciton polariton. The analysis yields the homogeneous linewidth and oscillator strength.
149 citations
TL;DR: In this paper, the development of an iron porphyrinate/axial ligand system that leads to control of the relative and absolute axial ligands orientations is described. The system consists of the iron(II1) complex of the hindered porphrin meso-tetramesitylprphyrin and pyridine ligands.
Abstract: The development of an iron porphyrinate/axial ligand system that leads to control of the relative and absolute axial ligand orientations is described. The system consists of the iron(II1) complex of the hindered porphyrin meso-tetramesitylprphyrin and pyridine ligands. The preparation and characterization of the low-spin (Fe(TMP)(4-NMe2Py),)CIO4 (4-NMe2Py = 4-(dimethy1amino)pyridine) derivative is described. The crystal structure determination shows that the complex has the desired relative perpendicular orientation of the two axial pyridines. The two pyridine planes are close to eclipsing adjacent Fe-C, vectors. The porphinato core is strongly S4-ruffled; the FeN, bonds show a commensurate shortening from the values expected for planar low-spin species. The EPR spectrum of the complex has a large g,, feature at 3.48 and no other discernible features. An analysis of the Mossbauer spectrum in a 6 T field allows estimation of a range of possible crystal field parameters (A/A = 1.9-3.6, VIA = 0.7-0.89). The complex displays the usual quadrupole doublet in zero field with an isomer shift of 0.20 and a quadrupole splitting of 1.74 mm/s. As discussed in the text, relatively low values of the quadrupole splitting constant appear characteristic of perpendicular orientations of the axial ligands in low-spin iron(II1). Two ucontroln complexes have also been prepared and characterized. The crystal structure of the bis(4-(dimethylamino)pyridine) derivative of (octa- ethylporphinato)iron(llI) shows that it has the normal parallel orientation of axial ligands and a normal low-spin rhombic EPR spectrum with g, = 2.8 18, g,, = 2.275, and g, = 1.630. Crystal field parameters for this complex have also been obtained from an analysis of the Mossbauer spectrum in a 6-T field. This complex also displays a quadrupole doublet in zero field with an isomer shift of 0.26 and quadrupole splitting of 2.14 mm/s. Bis( l-methylimidazole)(mes~tetramesitylpo~hinato)iron(III) has also been characterized; as expected, relative parallel orientations of axial ligands are found in the crystal structure as well as a planar porphyrin core. Mossbauer parameters are 6 = 0.28 mm/s and AE, = 2.28 mm/s. Crystal data: (Fe- (TMP)(4-NMelPy)2)C104.2CsH5Cl: a = 15.240 (3) A, b = 25.800 (6) A, c = 18.181 (4) A, fl = 97.72 (2)O, monoclinic, space group P2,/n, V = 7083.7 A', Z = 4, number of observed data = 6935, RI = 0.062, R2 = 0.071. (Fe(OEP)(4-
129 citations
TL;DR: In this paper, the authors describe the generation of magnetic fields in stars like the Sun by an azimuthally averaged dynamo model, which can be described by an Azimuthal averaged dynamos model.
Abstract: The generation of magnetic fields in stars like the Sun can be described by an azimuthally averaged dynamo model. Solutions of the linear (kinematic) problem have pure dipole or quadrupole symmetry, i.e. toroidal fields that are antisymmetric or symmetric about the equator. These symmetries can only be broken at bifurcations in the non-linear regime, which lead to the appearance of spatially asymmetric mixed-mode solutions. The symmetries of dipole, quadrupole and mixed-mode solutions, whether steady or periodic, form the same group for any axisymmetric dynamo. To establish the bifurcation structure it is necessary to follow unstable as well as stable solutions
86 citations
Journal Article•
TL;DR: In this paper, the gravitational quadrupole (and also the octupole and the hexadecapole) waves resulting from four different numerical collapse models for rotating 1.36 M −iron cores of 20 M −stars are calculated.
Abstract: The gravitational quadrupole (and also the octupole and the hexadecapole) waves resulting from four different numerical collapse models for rotating 1.36 M ○. −iron cores of 20 M ○. −stars are calculated. The gravitational dynamics of each core collapse is treated at the Newtonian level since the highest appearing values of the central density and the velocity are 2.6 10 14 g/cm 3 and 8 10 9 cm/s, respectively
62 citations
TL;DR: In this paper, the quadrupole coupling constant of the site responsible for the 30 ppm signal changes significantly with the degree of dealumination, from 4.5-5 MHz to > 6 MHz.
61 citations
TL;DR: In this article, the magnetic hyperfine parameters for B(2P) were studied using numerical multiconfiguration Hartree-Fock (MCHF) calculations and a newly developed finite-element MCHF program allowing very large configuration interaction expansions was used.
Abstract: The hyperfine parameters for B(2P) are studied using numerical multiconfiguration Hartree–Fock (MCHF) calculations. A newly developed finite‐element MCHF program allowing very large configuration–interaction expansions is used. The magnetic hyperfine parameters obtained are 0.0879(28), 0.7817(11), and −0.1675(3) a.u. for the Fermi contact term, the orbital term, and the spin–dipolar term, respectively, as compared to the experimental values of 0.1016(62), 0.7783(16), and −0.1686(5) a.u. The nuclear quadrupole moments obtained by comparing computed electric field gradients with experimental nuclear quadrupole couplings constants are Q(10B)=0.084 59(24) b and Q(11B)=0.040 59(10) b.
61 citations
TL;DR: Bulk properties like binding energies, rms radii, and quadrupole deformations of Ca, Ti, Cr, Fe, Ni, and Zn nuclei are calculated in the deformed relativistic mean field model.
Abstract: Bulk properties like binding energies, rms radii, and quadrupole deformations of Ca, Ti, Cr, Fe, Ni, and Zn nuclei are calculated in the deformed relativistic mean field model. Excellent results for the experimentally known binding energies and radii of nuclei are obtained. The calculation is extended to nuclei near the neutron-drip line. Dips in quadrupole deformation are seen for the known closed-shell configurations and enhanced deformations are obtained for specific neutron numbers.
61 citations
TL;DR: A random walk in velocity is implemented to bring the secular motion to a given temperature which is numerically measured.
Abstract: A molecular-dynamics simulation of hundreds of ions confined in a Paul trap has been performed. The simulation includes the trapped particles' micromotion and interparticle Coulomb interactions. A random walk in velocity was implemented to bring the secular motion to a given temperature which was numerically measured. When the coupling Gamma is large the ions from concentric shells which undergo a quadrupole oscillation at the RF frequency, while the ions within a shell form a 2D hexagonal lattice. Ion clouds at 5 mK show no RF heating for q(z) less than about 0.6, whereas rapid heating is seen for qz = 0.8.
56 citations
TL;DR: In this article, the hyperfine parameters for Be (2s2p; 3 P O) were obtained using numerical multiconfiguration Hartree-Fock (MCHF) calculations.
52 citations
TL;DR: In this article, a four-pole cell characterized by simplicity of design and applicability to reactive compounds under inert-atmosphere conditions, has been constructed and tested for measurements of dilute-solution field gradient induced birefringence.
Abstract: Improved equipment for measurements of dilute-solution field gradient induced birefringence, specifically a novel four-pole cell characterized by simplicity of design and applicability to reactive compounds under inert-atmosphere conditions, has been constructed and tested. A comparative study of the field gradient birefringence of benzene in three different cells (four-pole, monopole, and two-wire) and in two solvents (carbon tetrachloride and cyclohexane) is described, and a better value of the dilute-solution quadrupole moment of benzene (10 40 θ/C m 2 =−28.3±1.2) is reported
TL;DR: In this article, a pulsed-nozzle Fourier transform microwave spectrometer was used to study the rotational spectra of a rare gas-carbonyl sulfide complex.
Abstract: Pure rotational spectra of the mercury–carbonyl sulfide complex have been observed by a pulsed‐nozzle Fourier‐transform microwave spectrometer, which has been recently constructed. The structure of the complex is found to be T‐shaped, which is the same as the rare‐gas–carbonyl sulfide complexes analogous to this system. The mercury–carbon distance and the Hg–C–O angle have been determined to be 3.7075(2) A and 86.98(1) deg, respectively, for 202Hg–OCS from the rotational constants. Harmonic force constants of the van der Waals modes have been derived by the centrifugal distortion constants. The electric quadrupole coupling constants for 201Hg–OCS have also been determined and the values indicate small perturbation on the electric charge distribution of the mercury atom by complex formation.
TL;DR: In this paper, a different expression relating the birefringence to the quadrupole moment and other molecular properties is derived, using a recent eigenvalue theory of light propagation in matter.
Abstract: Measurement of the birefringence induced in a gas by an applied electric field gradient has been interpreted in terms of an existing molecular theory to yield the electric quadrupole moment of its molecules, whether dipolar or not. A different expression relating the birefringence to the quadrupole moment and other molecular properties is derived in the present paper, using a recent eigenvalue theory of light propagation in matter. Such an expression is required to be independent of molecular origin, even though a quadrupole moment depends in general on the choice of origin. The new result satisfies this requirement only if the primitive quadrupole moment, as opposed to the traceless, is used. In addition, it is shown that the earlier theory is inapplicable to the quadrupole moment experiment, in that it describes an incoherent phenomenon whereas birefringence is a coherent effect.
TL;DR: In this article, the electric polarizabilities, dipole and quadrupole moments of the molecules LiH, LiF, LiCl, NaH, NaF, NaCl, BeO, BeS, MgS, BeH, BeF, BeCl, mgH, mGF, mH, nGCl, LiO, LiS, NaO and NaS are computed in a uniform basis at correlated level of theory.
Abstract: Electric polarizabilities, dipole and quadrupole moments of the molecules LiH, LiF, LiCl, NaH, NaF, NaCl, BeO, BeS, MgO, MgS, BeH, BeF, BeCl, MgH, MgF, MgCl, LiO, LiS, NaO and NaS are computed in a uniform basis at the correlated level of theory. The results are rationalized in terms of the properties of ion pairs, and the stability of the isolated anions: the hydrides, oxides and sulphides show large and positive correlation corrections to the polarizability in CASSCF, and erratic convergence of the MBPT series. The open-shell alkaline-earth hydrides and halides in the series all exhibit negative polarizability anisotropy.
TL;DR: In this article, two γ-ray cascades with properties similar to those of the previously reported superdeformed bands in the heavier Hg isotopes have been identified as structures in 189Hg and 190Hg.
TL;DR: In this paper, the 28Si(58Ni, 2n)84Mo reaction has been studied at 195 MeV bombarding energy and the prompt gamma rays were detected in an array of twenty, escape-suppressed Ge detectors in coincidence with the recoiling nuclei, which were identified by A and Z with a recoil separator.
TL;DR: It has been shown that the bootstrap current in a stellarator can be externally controlled, and zero-current operation can be achieved.
Abstract: The toroidal current observed during electron cyclotron heating in the Advanced Toroidal Facility torsatron is identified as bootstrap current. The observed currents, ranging between +4 and {minus}2 kA, agree well with predictions of neoclassical theory in magnitude and parametric dependence, as determined by systematic scans of quadrupole (shaping) and dipole (magnetic axis shift) moments of the poloidal magnetic field. It has been shown that the bootstrap current in a stellarator can be externally controlled, and zero-current operation can be achieved.
TL;DR: In this article, the measurement of isotope shift and hyperfine splitting for the 723 nm atomic optical transition has been performed by combining the available muonic and electronic X-ray isotope shifts.
Abstract: We report here on the measurement of isotope shift and hyperfine splitting of190, 191, 193, 197Pb for the 723 nm atomic optical transition. Detailed analysis of the optical data has been done by combining them with the available muonic and electronicx-ray isotope shift data. The magnetic dipole moments and the electric quadrupole moments of the odd isotopes have been extracted from the hyperfine coupling constants of the atomic states involved in the optical transition used.
TL;DR: In this article, the authors performed a grand canonical Monte Carlo simulation for single-gas adsorption of Lennard-Jones molecules with point multipole moments in zeolite cavities of type X.
Abstract: Grand canonical Monte Carlo simulations have been performed for single-gas adsorption of Lennard-Jones molecules with point multipole moments in zeolite cavities of type X. Fluid-solid electrostatic interactions are taken into account. Adsorption isotherms, isosteric heats and structural properties have been calculated for Xe, CH4, CO2, C2H4 and i-C4H10 and compared with experiment. The results reveal the importance of adsorbate-adsorbate interactions for sorption in faujasite. The interaction of the quadrupole moment of CO2 with the electric field generated by the zeolite ions constitutes more than half of the total energy of adsorption. Density and energy distributions show that the cavity is either a relatively homogeneous surface or a highly heterogeneous one, depending on the molecular characteristics of the adsorbed gas and the type, position and charge of the zeolite cations.
TL;DR: In this article, the authors calculate the dependence of the giant dipole resonance (GDR) width on the nuclear quadrupole deformation and obtain a geometrical elliptic integral.
TL;DR: In this article, the electrophoretic motion of a non-Brownian rigid sphere with an arbitrary particle charge distribution was analyzed using the multipole expansion of the double-layer potential based on the linearized Poisson Boltzmann equation.
TL;DR: In this paper, the performance of medium-size polarized basis sets in calculations of molecular quadrupole moments is examined at the SCF and correlated levels of approximation for CH3OH, HCOOH and HCONH2.
Abstract: The performance of recently developed medium-size polarized basis sets in calculations of molecular quadrupole moments is examined at the SCF and correlated levels of approximation. The results for a series of small molecules are in good agreement with the data from large basis set calculations and with the experimental values. The computational approach suggests in this paper for calculations of molecular quadrupole moments is used to obtain trustworthy data for CH3OH, HCOOH and HCONH2. The magnitude and origin of the electron correlation contribution to molecular quadrupole moments and their implications for interaction potentials are discussed.
TL;DR: In this paper, the generator coordinate method for triaxial quadrupole collective motion is discussed and the collective solutions are classified according to the representations of the permutation group of the intrinsic axes.
TL;DR: In this paper, the rotational spectrum of the dinitrogen-acetylene dimer has been observed by pulsed-nozzle, Fourier transform microwave spectroscopy and the 14 N nuclear quadrupole coupling constants have been corrected for the effects of the angular oscillation of the N 2 subunit in the zero-point state of the dimer and for the electrical effect of the nearby acetylene subunit.
TL;DR: In this article, a simple procedure is presented for the determination of the asymmetry parameter of the electric field gradient, the quadrupole coupling constant, the second-order quadrupolar shift and the isotropic chemical shift of Quadrupolar nuclei with half-integer spin directly from the experimental magic angle spinning (MAS) NMR spectra of powder samples measured at a single magnetic field.
Abstract: A simple procedure is presented for the determination of the asymmetry parameter of the electric field gradient, the quadrupole coupling constant, the second-order quadrupolar shift and the isotropic chemical shift of quadrupolar nuclei with half-integer spin directly from the experimental magic angle spinning (MAS) NMR spectra of powder samples measured at a single magnetic field. General equations applicable to any half-integer spin nucleus and the specific expressions for 23Na and 27 Al are given. The simple calculations can easily be performed with a pocket calculator and avoid any spectral simulation or lengthy computer work. The method was applied to a series of 23Na MAS NMR spectra of selected sodium compounds and the agreement of the results with those of computer simulations is demonstrated.
TL;DR: In this paper, a spectrometer for measuring the nuclear quadrupole resonance spectra or the zero-field nuclear magnetic resonance spectras generated by a sample is disclosed, which uses an amplifier having a dc SQUID operating in a flux-locked loop for generating an amplified output as a function of the intensity of the signal generated by the sample.
TL;DR: In this paper, broad band emission of O2(b):M collision complexes was found to appear under the discrete rotational lines of the 0-0 band of the b1Σ a1Δg electric quadrupole transition at higher oxygen pressures and on addition of foreign gases.
Abstract: In flow tube studies of the quenching of O2(b1Σ), broad band emission of O2(b):M collision complexes was found to appear under the discrete rotational lines of the 0–0 band of the b1Σ a1Δg electric quadrupole transition at higher oxygen pressures and on addition of foreign gases. Bimolecular rate constants for the collision-induced emission processes have been derived from the ratio of the intensities of the discrete lines and the continuum as well as from low-resolution measurements of the relative intensities of the b a and b X bands as a function of O2 and added gas pressure. They range from ≈10−21 cm3 s−1 for He to ≈4 × 10−19 cm3 s−1 for PCl3 vapor.
TL;DR: In this paper, the pure rotation spectra of both H 79 Br and H 81 Br were recorded at Doppler resolution by means of tunable far-IR (TuFIR) spectroscopy.
TL;DR: In this article, the authors measured the self-broadening coefficients for 27 lines of acetylene in the P - and R -branch of the v 5 band at room temperature with a tunable diode-laser spectrometer.
Abstract: Self-broadening coefficients for 27 lines of acetylene in the P - and R -branches of the v 5 band have been measured at room temperature with a tunable diode-laser spectrometer. We have first calculated these broadening coefficients on the basis of two semi-classical impact models by using a simple intermolecular potential. The quadrupole moment of C 2 H 2 as well as a dispersion parameter have then been determined by fitting the calculated results of our experimental data. We next use the approach of Robert and Bonamy in which the intermolecular potential does not include adjustable parameters and involves the addition of an atom-atom interaction model to the electrostatic interactions. The usual spherical harmonics expansion of the atom-atom potential appears to be quite inadequate at short distances. The results of calculations derived from a rough consideration of the exact radial expansion of the atom-atom potential lead to better agreement for high J lines than those derived from the truncated expansion. It is also shown that the electrostatic contributions arising from the hexadecapole moment of C 2 H 2 are only significant for | m | > 20.
TL;DR: In this paper, the Coulomb scattering experiments initiated by unpolarized and aligned 7Li beams are reanalyzed and the electric moments of the particle-stable levels of 7Li, the spectroscopic quadrupole moment Qs of the ground state, its electric dipole polarizability τ11, the B(E2) value for excitation to the first excited state and the contribution τ12 to this excitation are determined.