Showing papers on "Quadrupole published in 1979"
TL;DR: In this paper, it was shown that rotational spin echoes provide a convenient means of studying very slow random molecular rotations (τc≲1 sec), which must be described by a proper average Hamiltonian theory.
Abstract: The NMR free induction decay from a spinning sample having inhomogeneous anisotropic interactions (chemical shifts, first order quadrupole couplings) takes the form of a train of rotational spin echoes. The Fourier transform of the echo envelope is a sharp spectrum from which the effects of anisotropy have been removed. The Fourier transform of the echo shape contains information concerning the anisotropies: This information can be extracted by a moment analysis. The effects of localized homonuclear spin–spin interactions are to convert the ’’isotropic’’ spectrum into a characteristic powder pattern. Second order quadrupole coupling produces a similar effect. It is shown in this case that the usual second‐order level shifts cannot be used to calculated this pattern, which must be described by a proper average Hamiltonian theory. Finally it is shown that rotational spin echoes provide a convenient means of studying very slow random molecular rotations (τc≲1 sec).
1,224 citations
TL;DR: Theoretical wavelengths, oscillator strengths, line strengths, and transition probabilities for the E1, M1, and E2 transitions among states with 2sn2pm configurations are presented for ions isoelectronic to the first-row atoms (Li through F) in this paper.
324 citations
TL;DR: The triple quadrupole mass spectrometer is shown to be a simple and highly efficient system for the observation of the fragmentation pattern of selected ions that is virtually eliminated by the selection of both parent and fragment ion.
Abstract: : The triple quadrupole mass spectrometer is shown to be a simple and highly efficient system for the observation of the fragmentation pattern of selected ions. The instrument consists of, in series, a CI/EI ion source, a quadrupole mass filter, an RF-only quadrupole collision chamber, a second mass filter, and an electron multiplier. The high sensitivity of the MS/MS technique with quadrupoles depends particularly on the highly efficient low energy collision-induced dissociation process in the strong focusing RF quadrupole field. Detection limits for methane and nitrobenzene of 10 to the minus 15 mole are shown. Analysis of a mixture of six components, including two isomers and an isobaric compound is presented. Chemical noise is virtually eliminated by the selection of both parent and fragment ion. An application of the system for structure elucidation is also described. (Author)
247 citations
TL;DR: In this paper, the results of digital simulation of ion trajectories in an RF-only quadrupole are presented, and the correspondence between simulated and experimental results aids in the understanding of the quadrupelle collision-induced dissociation (CID) process.
144 citations
TL;DR: In this paper, the effects of electron correlation on these molecular properties have been studied by performing generalized valence bond (perfect pairing) calculations with the same basis sets as were used in the Hartree-Fock calculations.
Abstract: Ab initio static polarizabilities, quadrupole moments, and electronic energies of ground state N2 and CO2 have been calculated self‐consistently as functions of nuclear geometry in the Hartree–Fock approximation using the finite‐field method. In addition, permanent dipole moments for the infrared‐active vibrational modes of CO2 have been determined. For N2, the effects of electron correlation on these molecular properties have been studied by performing generalized valence bond (perfect pairing) calculations with the same basis sets as were used in the Hartree–Fock calculations. These basis sets are constructed from energy‐optimized contracted sets of nucleus‐centered Gaussian‐orbitals to provide a flexible representation of the entire molecular charge cloud, including the highly polarizable outer regions. Results of these calculations are compared with experimental and other theoretical values where possible.
142 citations
TL;DR: In this article, the effect of the crystal environment is incorporated by the Watson sphere model, while consistency effects are included by a procedure adapted from many-body perturbation theory.
Abstract: Dipole and quadrupole polarizabilities have been studied for 40 closed-shell ions in crystals including the influence of both the environment in the crystal and self-consistency The effect of the crystal environment is incorporated by the Watson sphere model, while consistency effects are included by a procedure adapted from many-body perturbation theory Both effects are found to be of importance and, when included, lead to satisfactory agreement with available experimental data on dipole polarizabilities The influence of consistency effects is always found to reduce the polarizabilities with respect to the free ions while the influence of the crystal environment leads to a decrease for anions and an increase for cations Comparison is also made for free ions with experimental results, and with theoretical results from other approaches to focus on the accuracy of calculated consistency contributions Physical reasons are discussed for the observed trends in the various contributions to the polarizabilities for both free ions and ions in crystals
133 citations
TL;DR: In this paper, the electric field gradient along the molecular axis at the nucleus of the deuteron was calculated by means of the Ko\l{}os-Wolniewicz 54-term Born-Oppenheimer wave function.
Abstract: The electric field gradient along the molecular axis at the nucleus in ${\mathrm{D}}_{2}$ has been calculated at $R=1.4$ a.u. by means of the Ko\l{}os-Wolniewicz 54-term Born-Oppenheimer wave function. The result is a confirmation of the Reid-Vaida value. A nonadiabatic calculation using a 540-term wave function (explicitly containing the vibronic component) also confirms the earlier value of the electric field gradient and necessarily, therefore, the predicted quadrupole moment of the deuteron (i.e., $Q=0.2860\ifmmode\pm\else\textpm\fi{}0.0015$ ${\mathrm{fm}}^{2}$).
129 citations
TL;DR: In this article, the waveforms of the two polarizations at both frequencies were presented explicitly, and the amplitude of the precession amplitude was derived from observations of gravitational wave signals.
Abstract: An axially symmetric, torque-free rigid body, rotating and precessing, emits gravitational quadrupole radiation at two frequencies, omega and 2 omega, corresponding to the l = 2, m = 1,2 spherical harmonics. The paper presents explicitly the waveforms of the two polarizations at both frequencies. From observations of gravitational waves, one can derive information about the body's orientation and its precession amplitude. Electromagnetic radiation emitted by a spot fixed on the surface of the body arrives in pulses at a mean frequency Omega which is typically different from omega. If the body is not axially symmetric but the amplitude of the precession is small, the gravitational radiation at the lower frequency omega is split into two frequencies on either side of the electromagnetic pulse frequency. Explicit waveforms for the two polarizations in this case are also presented.
129 citations
76 citations
TL;DR: In this article, a model was developed for deformed nuclei in which their constituents, protons and neutrons, were described as axially symmetric rigid bodies, and two rotors, being free to rotate separately and interacting through a harmonic potential, performed intrinsic rotational oscillations with opposite phases about a common axis.
75 citations
TL;DR: In this article, the quadrupole moment and hexadecapole moment tensors, the diamagnetic contributions to the magnetizability tensors and the polarizable tensors of acetylene, ethylene and ethane are calculated using SCF wavefunctions close to the Hartree-Fock limit.
TL;DR: In this paper, the computation and fitting of an ab initio COH 2 potential energy surface is described and discussed, and the asymptotic forms of the electrostatic, induction and dispersion energies are presented; the dispersion energy calculated at long range yields the values of the parallel and perpendicular components of the quadrupole polarisability tensor, A, of the CO molecule.
TL;DR: In this paper, it is suggested that the ion condensation hypothesis, previously used for polyelectrolyte solutions, also describes the ion binding in lyotropic liquid crystals formed in mixtures of amphiphiles and water.
Abstract: It is suggested that the ion condensation hypothesis, previously used for polyelectrolyte solutions, also describes the ion binding in lyotropic liquid crystals formed in mixtures of amphiphiles and water. Counterion n.m.r. quadrupole splittings of these systems are shown to be appropriate for testing the ion condensation model. Data on 23Na+ quadrupole splittings are found to be in good agreement with the ion condensation approach. In particular, the effects of varying the water content, the concentration of added salt and the temperature are discussed. A previous conclusion concerning the thickness of the electrical double layer in lamellar liquid crystals is shown to be incorrect. The magnitude of the quadrupole splitting is estimated by means of a solution to the Poisson–Boltzmann equation obtained previously. Comparison with experimental data suggests that the field gradients at the nucleus are mainly determined by local effects.
TL;DR: In this paper, the authors used a shell model to calculate the surface relaxation of a semi-infinite MgO crystal and compared the results with a recent photoemission experiment as well as with LEED, EELS, and specific surface energy measurements.
Abstract: The relaxation of the (001) surface of a semi-infinite MgO crystal is calculated using a shell model. The model is borrowed from existing bulk studies but is modified so as to include three effects which arise from the presence of the surface and the considerable deformability of the oxygen ion: (a) environment-dependent variations in the anion polarizability, (b) quadrupole contributions to the total energy of the crystal, (c) overlap charge adjustments which alter the phenomenological model parameters near the surface. The results are compared with a recent photoemission experiment as well as with LEED, EELS, and specific surface energy measurements. An enhancement of the static effective ionic charge at the top layer relative to the bulk suggests itself as a dominant feature, the variable polarizability and quadrupole effects being largely suppressed in the static problem, However, all three effects may become important in the study of surface vibrations.
TL;DR: In this paper, the spectroscopic quadrupole moments (Qs) of the first two excited states and the B(E2) connecting these states to the ground state were determined.
01 Sep 1979
TL;DR: Isotope shifts and hyperfine structure of the BaI resonance line (λ=553.6 nm) have been measured by dye laser induced resonance fluorescence on an atomic beam for135m, 129g, 129m, 126Ba thus extending previous high resolution measurements of neutron deficient Ba nuclides (N<82) as mentioned in this paper.
Abstract: Isotope shifts and hyperfine structure of the BaI resonance-line (λ=553.6 nm) have been measured by dye laser induced resonance fluorescence on an atomic beam for135m, 129g, 129m, 126Ba thus extending previous high resolution measurements of neutron deficient Ba nuclides (N<82). The experimental results, now available for 16Ba isotopes and isomers withA=140−126, are used to deduce differences of rms charge radii, magnetic dipole and electric quadrupole moments. While the groundstates display a pronounced odd-even staggering the h 11/2− isomers135mBa and133mBa show a decreased staggering. Conspicuously the isomer shift of theg 7/2+ isomer129mBa proves to be negative. The nuclear structure information is discussed in the context of gammaspectroscopic studies of transitional nuclei with 50
TL;DR: In this article, the potential energy curves and quadrupole moment for the X 2 Σ + g, 2 ǫ + u, A 2 Π u, and 2ǫ g states of Li + 2 were presented.
TL;DR: In this paper, the dipole, quadrupole, octopole and hexadecapole moments, the electric field gradient at the oxygen nucleus, and the magnetizability and nuclear magnetic shielding tensors of the carbon monoxide molecule are calculated for a range of internuclear distances, using accurate SCF and configuration interaction wavefunctions.
TL;DR: In this paper, the authors measured particle spectra after Coulomb excitation of an enriched198Hg target with 4He and 16O beams, obtaining a positive quadrupole moment of Q2 = 0.66±0.18 eb (for negative interference) or Q2=0.80± 0.18 e2b2 (for positive interference).
Abstract: Reorientation effect and multiple Coulomb excitation measurements have been performed for198, 200, 202, 1204Hg. By measuring particle spectra after Coulomb excitation of an enriched198Hg target with4He and16O beams, a positive quadrupole moment of Q2 = 0.66±0.18 eb (for negative interference) or Q2=0.80±0.18 eb (for positive interference) andB(E2,0→2)=0.991±0.006 e2b2 were obtained. All otherB(E2) values and quadrupole moments were determined relative to these numbers from preciseγ-ray yields obtained from Coulomb excitation of a frozennatHg target with4He and16O projectiles. Oblate shapes of all Hg isotopes were found. The data have been interpreted in terms of triaxial rotation and anharmonic vibrations.
TL;DR: In this article, the authors measured the energies of the 4f → 3d, 3d → 2p and 2p → Is muonic atomic transitions in separated isotopes of 144, 148, 150, 152, 154 Sm.
TL;DR: In this article, a method was developed to analyze the beam dynamics of the radio frequency quadrupole accelerating structure, which can accept a dc beam at low velocity, bunch it with high capture efficiency, and accelerate it to a velocity suitable for injection into a drift tube linac.
Abstract: A method has been developed to analyze the beam dynamics of the radio frequency quadrupole accelerating structure. Calculations show that this structure can accept a dc beam at low velocity, bunch it with high capture efficiency, and accelerate it to a velocity suitable for injection into a drift tube linac.
TL;DR: In this article, the authors present results of a calculation of the low-lying collective quadrupole states in even-even nuclei within the framework of the proton-neutron interacting boson model.
TL;DR: In this article, a method of time delay operation of the r.f. quadrupole trap was investigated theoretically for trapping ions injected from external sources, and the results showed that the trap was able to trap ions from both external and internal sources.
TL;DR: In this paper, the 14N nuclear quadrupole resonance spectra for the compounds 2a, b, 3b, 4b, 5a, 6b have been obtained at 77 K and the asymmetry parameter and coupling constants extracted.
Abstract: Abstract The 14N nuclear quadrupole resonance spectra for the compounds 2a, b, 3b, 4b, 5a, b, 6b have been obtained at 77 K and the asymmetry parameter and coupling constants extracted. A comparison of these with microwave spectral results, shows that small but systematic differences occur between the solid and gaseous states. There is a high level of agreement for the observed coupling constants from NQR or MW spectra and the ab initio calculations in both magnitude and direction. This enables us to extract further principal axis data from the observed microwave spectra, and to predict with some confidence the axes and coupling magnitudes for other members of the series where incomplete determinations are available. Variations in coupling constants with structure are discussed
TL;DR: In this paper, the electric quadrupole moment of the particularly interesting nucleus was accurately determined: $Q(n = 0.065(20)$ b, b.
Abstract: Precision hyperfine-structure measurements in the $4s4p^{3}P_{2}$ metastable state of $^{43}\mathrm{Ca}$ were performed using the atomic-beam magnetic-resonance method combined with a single-mode dye laser for the detection. For the first time the electric quadrupole moment of the particularly interesting $^{43}\mathrm{Ca}$ nucleus was accurately determined: $Q(^{43}\mathrm{Ca})=\ensuremath{-}0.065(20)$ b. In addition, isotope shifts and hyperfine structure in the transition $4s4p^{3}P_{2}\ensuremath{\leftrightarrow}4s5s^{3}S_{1}$ were obtained using high-resolution laser spectroscopy.
TL;DR: In this paper, the inverse reaction 24 Mg( 136 Xe, 4n) 156 Dy at 595 MeV has been used to populate high spin states in 156 Dy.
TL;DR: In this paper, the lattice vibration frequencies of benzene and naphthalene have been calculated using quadrupole interactions, in which quadrupoles have been added to the usual atom terms.
TL;DR: Using accurate SCF wavefunctions, the quadrupole and hexadecapole moments and the elements of the polarizability tensor of the carbon disulphide molecule were calculated in this article.
TL;DR: In this paper, measurements of the microwave spectrum of BrF were carried out on the hyperfine components of J = 1 ← 0 and J = 2 ← 1 rotational transitions of 79 BrF and 81 BrF.
TL;DR: In this article, it was shown that several two-body unitary transformations which arise in the theory of meson exchange currents can change the percentage $D$ state of the deuteron, implying that this percentage is not a measurable quantity.
Abstract: It is shown that several two-body unitary transformations which arise in the theory of meson-exchange currents can change the percentage $D$ state of the deuteron, implying that this percentage is not a measurable quantity. The connection of these transformations to meson-exchange contributions to the quadrupole moment, rms radius, magnetic moment, and the asymptotic $\frac{D}{S}$ ratio of the deuteron is discussed.NUCLEAR STRUCTURE $^{2}\mathrm{H}$; $q$, $\ensuremath{\mu}$, $\ensuremath{\rho}$; meson-exchange currents; percent $D$ state.