Showing papers on "Quadrupole published in 1974"
TL;DR: In this article, the ΔJ = 0,l-doublet transitions of OCS isotopes (16O12C32S, 16O 12C33S and 16O12c34S) in the (0110) vibrational state have been measured in a molecular-beam electric-resonance spectrometer equipped with a nozzle source.
190 citations
TL;DR: In this paper, the microwave spectra of two ring-substituted species of pyridine have been remeasured and the remaining two remaining species investigated and assigned.
143 citations
TL;DR: In this article, the potential energy surface of the H3+ ion has been calculated using generalized Morse functions and Fourier analysis, and an analysis of the equilibrium geometry and harmonic force constants is presented.
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.
123 citations
TL;DR: In this paper, a broad discussion of the ground-state potential-energy surfaces of doubly even deformed and transitional nuclei with Z = 50−82 is presented, where the surfaces are calculated microscopically as functions of the quadrupole axial e and non-axial γ and the axial hexadecapole e4 deformations.
112 citations
TL;DR: In this article, the coulombic correlation of induced electric dipoles in the ligands by the transition quadrupole moment of the metal ion was found to give a nonzero resultant electric dipole transition moment in complexes devoid of inversion symmetry or S p axes for p > 5.
110 citations
TL;DR: In this article, the 14N and 2D pure quadrupole resonance has been measured at 77 K in 19 deuterated amino acids and several other compounds, in all cases the shifts can be accounted for by a decrease in charge along the NH bonds.
108 citations
104 citations
TL;DR: In this article, the intermolecular potentials for D2, N2, O2, F2 and CO2 are determined on the basis of the second virial coeffincients, the polarizabilities parallel and perpendicular to the molecular axes, and the electric quadrupole moment.
99 citations
TL;DR: In this paper, a set of experimental data concerning the giant dipole resonance of nuclei (GDR) in the 103 ≦ A ≦ 133 mass region was presented, and it was shown that the width of the GDR increases as β increases and as E 2+ decreases and that theoretically predicted spreading of the dipole strength is confirmed by their experimental results.
98 citations
TL;DR: In this paper, the Hartree-Bogolyubov treatment of the pairing-plus-quadrupole model, employed previously for the energy levels and the electromagnetic moments of W, Os and Pt nuclei, has been modified and extended to higher angular momentum states.
98 citations
TL;DR: Using ab initio wave functions and the full operators, dipole and second moments are reported for a number of five and six-membered ring heterocycles containing the elements nitrogen, oxygen, sulphur, and phosphorus as discussed by the authors.
Abstract: Using ab initio wave functions and the full operators, dipole and second moments are reported for a number of five- and six-membered ring heterocycles containing the elements nitrogen, oxygen, sulphur, and phosphorus. The agreement with experiment is satisfactory and a linear relationship µexptl.= 0·952µcalc. is obtained with an average error of 0·29 D. With the exception of the quadrupole moments, the second moments are just outside the experimental error in the worst cases. Population analyses for the compounds are found to be additive in bond contributions, and this assists in the interpretation of the σ- and π-dipole moments. The difference in average position between the valency shell π-electrons has been related to aromatic character.
TL;DR: In this article, a comparison of the Mossbauer spectra of deoxy Hb•A and its isolated α and β subunits was carried out over the temperature range 77-200°K.
Abstract: A comparison study of the Mossbauer spectra of deoxy Hb‐A (low oxygen affinity) and its isolated α and β subunits (high oxygen affinity) was carried out over the temperature range 77–200°K. Within experimental error, no difference was detected between these three proteins, either in the isomeric shifts or in the quadrupole splittings. These results show that the characteristically different oxygen affinity of deoxy Hb‐A and its isolated subunits is not a consequence of different electronic states for the ferrous ions in Hb‐A and its isolated subunits. The electronic structure of the ferrous ion in hemoglobin was determined using a crystal field approximation. The adjustable parameters in the crystal field model were systematically searched for an electronic level configuration that would give good agreement with the experimental data of the temperature‐dependent quadrupole splitting and magnetic susceptibility of deoxy Hb‐A. The resulting low lying energy levels in order of increasing energy were 5B2, 1A1, 5E, and 3E. The spin and orbital degeneracy of these levels were removed by the spin‐orbit interaction and the rhombic perturbation of the crystalline field. The electronic ground state obtained produces an electric field gradient at the iron nucleus with a principal component of 0.11 e parallel to the heme plane and an asymmetry parameter η = 0.51.
TL;DR: In this article, the deuterated and 15 N species of pyrazole were compared to crystal structures derived by X-ray and neutron diffraction showing the N-H bond in the crystal to be prolonged, but no significant differences seem to develop when bringing the molecule from its isolated state into the crystal with its strong hydrogen bonds.
TL;DR: In this paper, the inelastic collisions of a heavy fast particle of charge with an electron bound in an atom isotropically and harmonically is considered, and two methods are employed to calculate the contributions to the mean energy loss and the excitation probabilities due to dipole and quadrupole terms in the multipole expansion.
Abstract: The inelastic collisions of a heavy fast particle of charge ${Z}_{1}e$, incident at an impact parameter $b$, with an electron bound in an atom isotropically and harmonically is considered. The "atom" is treated by quantum mechanics, extending an earlier classical calculation by Ashley, Ritchie, and Brandt. A multiople of the Coulomb interaction for distanct collisions is used. Two methods are employed to calculate ${Z}_{1}^{3}$ contributions to the mean energy loss and the excitation probabilities due to dipole and quadrupole terms in the multipole expansion. In one method the dipole interaction is taken into account exactly by applying the quantum formalism of the forced harmonic oscillator, and the quadrupole interaction is treated as first-order perturbation. The second method of calculation employs both dipole and quadrupole interactions as time-dependent perturbations to second order on the free harmonic oscillator. The energy loss calculated for a particle incident on a straight-line trajectory agrees with the classical calculation. Reasons for this agreement are goven. Simplifications of the calculation owing to time-reversal symmetry considerations and selection rules for the harmonic oscillator are discussed. Comments are made concerning the relative importance of distant and close collisions at high and low velocities.
TL;DR: In this article, quadrupole moments obtained with multiconfiguration self-consistent field wavefunctions chosen by the optimized valence configuration approach of Wahl and Das were compared with both the experimental and Hartree-Fock values.
Abstract: Quadrupole moments obtained by a variety of experiments exhibit a wide range of values even for molecules such as CO and N2. Previous theoretical values were obtained with Hartree‐Fock single‐configuration wavefunctions. This study reports quadrupole moments obtained with multiconfiguration self‐consistent‐field wavefunctions chosen by the optimized valence configuration approach of Wahl and Das. The theoretical MC‐SCF quadrupole moments are compared with both the experimental and Hartree‐Fock values. Vibrationally averaged values of the quadrupole moments were obtained for CO and NO+. The results for the ν=0, J=0 vibrational level are −2.23 and 0.56×10−26 esu cm2, respectively.
TL;DR: In this paper, single crystal rotation spectra have been obtained for the 13C resonance in K2Pt(CN)4Br0.3 · 3H2O and 13C chemical shift tensor determined.
Abstract: Single crystal rotation spectra have been obtained for the 13C resonance in K2Pt(CN)4Br0.3 · 3H2O and the 13C chemical shift tensor determined. The principal values are (relative to the carboxyl carbon in CH3COOH): σ11=261±10 ppm (parallel to C–N bond), σ22 = −48±10 ppm (perpendicular to C–N bond and Pt–Pt chain), and σ33=−10±5 ppm (parallel to Pt–Pt direction). Since the 14N quadrupole interaction is of similar size to the 14N Zeeman interaction in this material, large effects of the 14N quadrupole interaction are observed on the 13C spectra.
TL;DR: In this article, the use of matrix methods to calculate ion displacements in quadrupole fields is applied to a detailed simulation of mass filter operation, and ion transmission is calculated for various scan lines and various apertures both with and without fringing fields.
TL;DR: In this paper, cross sections for excitations of the three fundamental vibrational modes of H 2 O by electron collisions are calculated with the use of the Born theory for the collision energies from the threshold to 100 eV.
Abstract: Cross sections for excitations of the three fundamental vibrational modes of H 2 O by electron collisions are calculated with the use of the Born theory for the collision energies from the threshold to 100 eV. Electron-molecular multipole (dipole and quadrupole) interactions, as well as polarization force, are taken into account. The dominance of the quadrupole interaction relative to the dipole one prevents the cross section from falling rapidly as the energy increases, resulting in a fairly large cross section even in the high energy range (\({\gtrsim}10\) eV). Differential cross sections are also calculated at 1, 15, and 53 eV. For the latter two incident energies, a comparison is made with the relative differential cross section measured by Trajmar et al.
TL;DR: In this article, the effect of spin lattice relaxation rates on pure quadrupole resonance pulse experiments for spins with I = 1 is given, in which the three dimensional relaxation problem is reduced to a two dimensional one.
Abstract: A quantitative analysis of the effect of spin lattice relaxation rates on pure quadrupole resonance pulse experiments for spins with I = 1 is given. A model is presented in which the three dimensional relaxation problem is reduced to a two dimensional one. In this model any possible population distribution of the energy levels corresponds to a point in a plane, the ``ν plane.'' The response of the system to spin‐lattice relaxation effects and to rf pulses are described as translations of points in this plane. The experimental signal intensities are directly related to the coordinates of those points. The following cases are treated quantitatively: (i) CW saturation, (ii) CW saturation followed by a 90° pulse, (iii) two‐pulse sequences, and (iv) continuous steady state pulse sequences. For each case explicit equations for the signal intensity as function of the experimental parameters are given. The analysis is made for both single crystals and powders.
CERN1
TL;DR: In this article, the energy and intensities of 53 nuclear γ-lines in muonic atoms of Sm, Gd, Eu, Tm, Yb, Ta, W, Re, Os, Ir, Pt, Hg, Tl, and Bi have been measured with Ge(Li) detectors.
TL;DR: In this article, the authors used the weak-coupling model in order to analyze the hyperfine structure of 197Au and reported the measurement of the energies of various muonic atomic transitions above 500 keV.
TL;DR: In this paper, the paramagnetic magnetizability and rotational g value function for hydrogen are extracted from published experimental data and combination of the latter with an accurate calculation of the quadrupole moment leads to precise values of the magnetizerability anisotropy for the lower vibration-rotation states of hydrogen.
Abstract: It is commonly assumed that the nuclei are at a fixed separation when relating the electric quadrupole moment of a diatomic molecule in a 1Σ state to the rotational g value and the magnetizability anisotropy. This assumption is examined with particular reference to the hydrogen isotopes and is found to lead to an error of approximately 1 per cent in the quadrupole moment. The paramagnetic magnetizability and rotational g value function for hydrogen are extracted from published experimental data and combination of the latter with an accurate calculation of the quadrupole moment leads to precise values of the magnetizability anisotropy for the lower vibration-rotation states of hydrogen. An experimental measurement of the rotational g value for just one further state or isotope of hydrogen is required to make the analysis more accurate.
TL;DR: In this article, the nuclear electric quadrupole interaction parameters (coupling constant and asymmetry) and the several anisotropic Knight shift parameters of the 51V, 59Co, and 93Nb nuclear magnetic resonance spectra in VB, CoB, and NbB monoborides, respectively.
Abstract: Measurements are reported of the nuclear electric quadrupole interaction parameters (coupling constant and asymmetry) and the several anisotropic Knight shift parameters of the 51V, 59Co, and 93Nb nuclear magnetic resonance spectra in VB, CoB, and NbB monoborides, respectively. A detailed account is given of the method of extracting these parameters from the experimental spectra. The quadrupole coupling constants and asymmetry parameters are 51VB, 1.75 MHz, 0.95; 59CoB, 25.2 MHz, 0.74; and 93NbB, 20.4 MHz, 0.065. The isotropic components of the Knight shifts are all positive: 51VB, 0.32%; 59CoB, 0.69%; and 93NbB, 0.24%. Despite the close similarity in the structures of these compounds, neither the quadrupole nor Knight shift parameters scale in a simple manner with the nuclear properties. Thus, even in the cases of VB and NbB, it appears that a rigid‐band type approximation furnishes a poor description of the actual changes in the electronic structure.
TL;DR: In this paper, the electronic wavefunctions for the ground (X1 Σ+) and the low-lying excited states (a3Π, A1Π and 3Σ+) of the BH molecule have been calculated as a function of internuclear distance using the ab initio generalized valence bond method (GVB) with optimization of spin coupling (SOGI).
TL;DR: For the ground state, a variety of basis sets were used, the largest being an uncontracted Gaussian basis: C(11s 7p 2d), O(11 s 7p 3d), H(6s 1p) as mentioned in this paper.
Abstract: Ab initio self‐consistent‐field wavefunctions and molecular properties have been calculated for the three lowest electronic states of H2CO. For the ground state, a variety of basis sets were used, the largest being an uncontracted Gaussian basis: C(11s 7p 2d), O(11s 7p 2d), H(6s 1p). For the excited states, the above basis was contracted to C(7s 5p 2d), O(7s 5p 2d), H(4s 1p). Ground state molecular properties agree well with the earlier theoretical study of Neumann and Moskowitz, and with available experimental data. The z components (along the CO bond axis) of the excited state dipole moments have been measured, and the present a priori predictions reproduce experiment rather closely. Other properties reported include quadrupole moments, octupole moments, and electric field gradients.
TL;DR: In this article, the zero-field microwave spectra of the J =0 → J = 1 transitions in H11B32S, D11B 32S, and D10B32s have been observed under high resolution to give the boron nuclear quadrupole coupling constants of eqQ = −3.72±0.03 MHz for 11B and eqQ= −7.91± 0.03MHz for 10B and the nuclear magnetic spin rotation constants along the axis perpendicular to the internuclear axis of M⊥=−7.
Abstract: The zero‐field microwave spectra of the J =0 → J = 1 transitions in H11B32S, D11B32S, and D10B32S have been observed under high resolution to give the boron nuclear quadrupole coupling constants of eqQ = −3.72±0.03 MHz for 11B and eqQ = −7.91±0.03 MHz for 10B and the nuclear magnetic spin rotation constants along the axis perpendicular to the internuclear axis of M⊥=−7.2 ± 3.0 kHz for 11B and 1M⊥=−2.6 ± 1.0 kHz for 10B. The magnitude of the electric dipole moment was measured by high electric fields (Stark effect) to give |μ| = 1.298 ± 0.005 D. High magnetic fields (Zeeman effect) were used to measure the molecular g values and magnetic susceptibility anisotropies. The results are g⊥=−0.0414 ± 0.0002 and χ⊥−χ∥=7.2 ± 0.5 × 10−6 erg/G2· mole for H11B32S and g⊥=−0.0356 ± 0.0002 and χ⊥−χ∥=9.8 ± 2.1 × 10−6 erg/G2· mole for D11B32S. The resultant molecular electric quadrupole moment is Q∥ =2.7±0.6 × 10−26 esu · cm2 and the g values from the H11B32S–D11B32S isotopic pair were used to determine the sign of the el...
TL;DR: In this article, the microwave spectra of CD3CH2CN, CH3CD2CN and CH3C15N have been measured and a complete rs-structure has been calculated by the equations of Kraitchman and Chutjian.
Abstract: The microwave spectra of CD3CH2CN, 13CH3CH2CN, CH313CH2CN and CH3CH2C15N have been measured. In addition the spectrum of CH3CH213CN has been remeasured with greater accuracy. From these spectra and those previously reported - CH3CH2CN, CH3CD2CN, CH2DCH2CN (sym) and CH2DCH2CN (asym) - a complete rs-structure has been calculated by the equations of Kraitchman and Chutjian. r0-structure calculations were performed with different assumptions due to the symmetry of the molecule. A comparison between r0- and rs-structure was made and showed good agreement especially for the atoms of the frame. The quadrupole coupling constants of the above mentioned isotopes of ethyl cyanide were obtained from the hyperfine structure of the spectra with the exception of CH3CH2C15N, which has no nucleus with quadrupole moment. The quadrupole coupling tensor in its principal axis system was determined from the constants of CD3CH2CN and CH3CD2CN using the angle e between their principal axes of inertia in the a-b-plane. From Stark effect measurements the dipole moment of CH3CH2CN was reevaluated. To determine the direction of the dipole moment Stark effect measurements for CD3CH2CN and CH3CD2CN were carried out.
TL;DR: In this article, the phase diagrams of vanadium-hydrogen (V-H) and vanadium deuterium (D) were investigated by measuring the nuclear magnetic resonance (NMR) spectra of V-H and V-D in strongly textured vanadium foils.