Showing papers on "Quadrupole published in 1984"
Book•
01 Jan 1984
TL;DR: Theoretical Aspects of molecular Rotation Microwave Transitions - Line Intensities and Shapes Diatomic Molecules Linear Polyatomic Molecules Symmetric-Top Molecules Asymmetric-top Molecules The Distortable Rotor Nuclear Hyperfine Structure in Molecular Rotational Spectra effects of Applied Electric Fields Effects of Applied Magnetic Fields Internal Motions Derivation of Molecular Structures Quadrupole Couplings, Dipole Moments, and the Chemical Bond Irreducible Tensor Methods for Calculation of Complex Spectra Appendixes Author Index Subject Index
Abstract: Introduction Theoretical Aspects of Molecular Rotation Microwave Transitions - Line Intensities and Shapes Diatomic Molecules Linear Polyatomic Molecules Symmetric-Top Molecules Asymmetric-Top Molecules The Distortable Rotor Nuclear Hyperfine Structure in Molecular Rotational Spectra Effects of Applied Electric Fields Effects of Applied Magnetic Fields Internal Motions Derivation of Molecular Structures Quadrupole Couplings, Dipole Moments, and the Chemical Bond Irreducible Tensor Methods for Calculation of Complex Spectra Appendixes Author Index Subject Index.
1,881 citations
TL;DR: In this article, the intensity of a half-integer spin nucleus subject only to the quadrupolar interaction is calculated as a function of the length τ of the on-resonance excitation pulse and quadrupole coupling paramters.
192 citations
Book•
01 Dec 1984
TL;DR: In this paper, the authors present the theory of quadrupole focusing with the practical development of micro-probe systems in mind, and assess the importance of various effects by reference to their influence in three existing microprobe system.
Abstract: This book presents the theory of quadrupole focusing with the practical development of microprobe systems in mind. The introductory chapter outlines the analytical processes and provides a background to the problems of designing quadrupole probe-forming systems. Following a description of the quadrupole lens and the mathematical models used to describe the fields within both magnetic and electrostatic quadrupole lenses, the authors describe two techniques for calculating the path of a charged particle through a beam-optical system; matrix methods and numerical raytracing. The minimum spot size achieved by a quadrupole system is influenced strongly by parasitic aberrations due to imperfections in the construction and alignment of the instrument. The authors assess the importance of the various effects by reference to their influence in three existing microprobe systems. Finally, they describe briefly some novel and interesting alternatives to the quadrupole lens as the focusing element. Refs.
152 citations
TL;DR: In this paper, the radio frequency and microwave spectra of H2O-CO2 and D2O−CO2 have been measured by molecular beam electric resonance spectroscopy, where rotational constants, deuterium quadrupole coupling constants, and dipole moments are reported.
Abstract: The radio frequency and microwave spectra of H2O–CO2, HDO–CO2, and D2O–CO2 have been measured by molecular beam electric resonance spectroscopy. Rotational constants, deuterium quadrupole coupling constants, and dipole moments are reported.
147 citations
TL;DR: In this article, the pseudopotential results for Cu2, Ag2, CuH, and AgH were refined in two ways: (i) the density functional approximation for valence correlation is replaced by a CI treatment, and (ii) the dipole polarization potential describing core-valence correlation was supplemented by a quadrupole correction term.
Abstract: Our recent pseudopotential results for Cu2, Ag2, CuH, and AgH [J. Chem. Phys. 79, 5532 (1983)] are refined in two ways: (i) the density‐functional approximation for valence correlation is replaced by a CI treatment, and (ii) the dipole polarization potential describing core‐valence correlation is supplemented by a quadrupole correction term.
104 citations
TL;DR: In this article, the nuclear response function of 40Ca was studied at finite temperature using self-consistent RPA and it was shown that the isovector dipole strength function is quite independent of temperature up to T≈6 MeV.
86 citations
TL;DR: In this article, the electric field gradients at the nuclei in LiH are calculated by combining fully numerical and discrete basis set methods, and the present lithium quadrupole moments are Q ( 6 Li) = −0.00083 b and Q ( 7 Li) < 0.0406 b.
68 citations
01 Jan 1984
TL;DR: In this paper, the authors used the seeded-beam technique to produce a supersonic beam with strong translational, rotational and vibrational cooling for the sodium cyanide molecule.
Abstract: The sodium cyanide molecule was studied by molecular-beam electric-resonance spectroscopy in the microwave region. We used the seeded-beam technique to produce a supersonic beam with strong translational, rotational and vibrational cooling. In the frequency range 9.5–40 GHz we observed and identified for NaCN 186 and for Na13CN 107 hyperfine transitions in 20 and 16 rotational transitions, respectively, all in the ground vibrational state. The rotational, the five quartic and three sextic centrifugal distortion constants of NaCN are: A″ = 57921.954(7) MHz; B″ = 8369.312(2) MHz, C″ = 7272.712(2) MHz. All quadrupole and several spin-rotation coupling constants for the hyperfine interaction were evaluated. The quadrupole coupling constants (in MHz) for NaCN are: eQq12(Na) = −5.344(5), eQq12 = 2.397(7). eQq12(N) = 2.148(4), eQq12(N) = −4.142(5). From these constants and those of Na13CN we have determined the principal components of the quadrupole coupling tensor for potassium and nitrogen. The structure of sodium cyanide evaluated from the rotational constants of NaCN and Na13CN was found to be T shaped, similar to the structure of KCN but completely different from the linear isocyanide configuration of LiNC. The effective structural parameters for sodium cyanide in the ground vibrational state are: rCN = 1.170(4) A, rNaC = 2.379(15) A, rN12N = 2.233(15) A, in gratifying agreement with ab initio calculations. Both the geometrical structure and the hyperfine coupling justify the conclusion that the CN group in gaseous sodium cyanide approximately can be considered as a free CN− ion.
67 citations
TL;DR: In this paper, the dipole and quadrupole derivatives of H2O and H2S are calculated analytically, using the coupled Hartree-Fock method first proposed by Gerratt and Mills.
63 citations
57 citations
TL;DR: In this article, the core-polarization effect on the 1s0d-shell single-particle electromagnetic quadrupole transitions due to coupling with the quadrupoles giant resonances was studied.
TL;DR: In this paper, a new pulse sequence which refocuses both the dipolar and quadrupole interactions is suggested, which is based on the quadrupolar split powder pattern is no longer symmetric about the center of the spectrum.
TL;DR: In this paper, the electron spin echo envelope modulation method was used to determine the 14N hyperfine and quadrupole interaction tensors in the lowest photo-excited triplet state of freebase porphin in an n-octane single crystal at ∼14 K.
Abstract: Through the use of the electron spin echo envelope modulation method, we have accomplished the complete determination of the 14N hyperfine and quadrupole interaction tensors in the lowest photo‐excited triplet state of free‐base porphin in an n‐octane single crystal at ∼14 K The results give insight into the molecular structure of the porphin in the excited state, the relationship between the nitrogen spin density and observed hyperfine couplings, and the effect of hydrogen bonding interactions on the quadrupole coupling constants and principal axes
TL;DR: In this paper, the authors analyse the structure of the electric field tensor from the point of view of the quadrupole splittings and the contributions of dipolar terms to the internal field.
Abstract: Mossbauer experiments on amorphous materials generally show an asymmetry often attributed to quadrupole splitting effects. On the other hand, some amorphous structures can be simulated with a soft-sphere relaxed model. The authors analyse this structure from the point of view of the electric field tensor, and look at the resulting distribution law for the quadrupole splittings and the contributions of dipolar terms to the internal field. By considering further a distribution of internal fields, a very simple model for analysing Mossbauer spectra is given and discussed.
CERN1
TL;DR: In this article, the low energy deuteron parameters are discussed in view of their physical information and their constraints on the description of the deuterons in terms of more exotic subsystems, and strong evidence is found for quantitative dominance of pionic interactions, particularly for the D S ratio and quadrupole moment.
TL;DR: In this article, the quadratic hypernetted chain integral equation (LHNC) and tetrahedral quadrupole tensor (TQT) were solved for water with permanent dipoles and quadrupoles moments similar to those of the water molecule.
Abstract: In this paper we present molecular dynamics (MD) results for fluids of Lennard-Jones particles with permanent dipole and quadrupole moments similar to those of the water molecule. We consider both the true quadrupole tensor of water and the tetrahedral quadrupole approximation which is convenient in theoretical work. The linearized and quadratic hypernettedchain (LHNC and QHNC) integral equation approximations are solved for the tetrahedral quadrupole model and detailed comparisons are made with the MD calculations. It is found that both theories are more accurate at relatively high densities with the QHNC giving better results for most fluid properties.
TL;DR: In this paper, the rotational population distributions for N 2 and N 2 + in a pulsed supersonic expansion were obtained from two-photon laser-induced fluorescence spectra of the a 1 Π g ← X 1 Σ g + transition.
TL;DR: In this article, it was shown that the charge-current operator for the quadrupole (N→ Δ ) transition violates gauge invariance for the nonrelativistic constituent quark model, which is related to the behaviour of the two operators under hermitean conjugation and time reversal.
TL;DR: In this paper, partial quadrupole splitting theory was used to calculate the splittings for individual next-nearest neighbor configurations in the Mossbauer spectra of synthetic chromite-hercynite spinels.
TL;DR: In this article, a contact transformation method was used to determine higher-order corrections to the harmonic oscillator and rigid rotor energy levels of molecules, analogous centrifugal distortion and anharmonic correction to the nuclear quadrupole coupling energies for molecules containing one quadrupolar nucleus.
TL;DR: In this article, a theory for the second term of the series representing the asymptotic atom-surface interaction is presented, with the quadrupole polarizability y replacing the dipole polarizer α.
TL;DR: The alignment determined from rotationally resolved CN emission following CICN photodissociation does not describe the quadrupole moment of the nuclear as mentioned in this paper, which is not the case in this paper.
TL;DR: In this paper, the quadrupole mass filter can be operated in a stability region at a much higher q value than that normally used, which requires a high r.f. frequency and only a very small d.c. voltage.
TL;DR: In this article, a theoretical analysis based on the magnetohydrodynamic approximation is carried out on the effect of multipole field suppression of the rotational instabilities excited in a high-β plasma column.
Abstract: A theoretical analysis based on the magnetohydrodynamic approximation is carried out on the effect of multipole‐field suppression of the rotational instabilities excited in a high‐β plasma column. The multipole field is assumed not to penetrate into the plasma column but to exert magnetic pressure on its boundary surface in order to suppress the distortion of the plasma column. Analytical theory, which takes into account only the effects of the fundamental wave, gives the stability criterion for the n=2 mode as Bs≥Bs,c= 1/2 (m−1)−1/2rs‖Ω‖(μ0 ρ0)1/2, where rs, ρ0, and Ω are the radius, mass density, and rotational angular velocity of the plasma column, respectively, 2m the order of the multipole field, Bs the field strength at radius rs in the vacuum state, and μ0 the permeability of vacuum. Numerical calculations including the effects of the waves parasitic to the fundamental wave support the stability criterion for hexapole (m=3) and octopole (m=4) fields. For quadrupole (m=2) fields, it is shown that the stable range of Bs is limited between 0.841 Bs,c and 0.856 Bs,c, where Bs,c is the analytical threshold for m=2.
TL;DR: In this paper, the radiation resulting from 15keV-electron bombardment of thin silver films and of particles formed by heat treating these films were treated as oblate and prolate spheroids on which resonant surface charge-density oscillations (surface plasmons) were excited by electron bombardment.
Abstract: We have studied the radiation resulting from 15keV-electron bombardment of thin silver films and of particles formed by heat treating these films. The particles were treated as oblate and prolate spheroids on which resonant surface-charge-density oscillations (surface plasmons) were excited by electron bombardment. We have calculated the energy associated with various surface-plasmon modes as a function of the shape of the spheroid using nonretarded electrodynamics and the optical properties of bulk silver. We have obtained good agreement between the calculations and the experimental observations of the wavelength, polarization, and angular intensity distributions of radiation emitted by silver particles which were characterized as to size and shape with the use of scanning electron microscopy. The emission from one type of sample was found to be the result of the radiative decay of a dipole and a quadrupole oscillation on oblate spheroids. The radiation from another type of sample showed evidence of the decay of dipole plasmons on prolate particles.
TL;DR: In this article, self-consistent cranking HFB calculations including quadrupole pairing are performed for all those experimentally known rotational bands in the rare-earth mass region which are expected to be specifically influenced by the pair field of multipolarity 2.
TL;DR: Based on the calculated electric field gradient (q) from ab initio CI wavefunctions and the experimental nuclear quadrupole coupling constant (e2Qq) for nitrogen in NH3, an improved value of the 14N nucleus was proposed as Q(14N) = 1.95 × 10−26 cm2 as mentioned in this paper.
TL;DR: In this paper, the Fourier transform of pure NQR was observed by pulsed field cycling for deuterium and well resolved spectra were obtained with high sensitivity showing the low frequency nu0 lines and allowing assignments of quadrupole couplings and asymmetry parameters to inequivalent deuterons.
Abstract: We report the observation of Fourier transform pure NQR by pulsed field cycling. For deuterium, well resolved spectra are obtained with high sensitivity showing the low frequency nu0 lines and allowing assignments of quadrupole couplings and asymmetry parameters to inequivalent deuterons. The technique is ideally applicable to nuclei with low quadrupolar frequencies (e.g., 2D, 7Li, 11B, 27Al, 23Na, 14N) and makes possible high resolution structure determination in polycrystalline or disordered materials.
TL;DR: In this article, condensed coherent fermion pairs have a property that each pair can be treated as if it is independent of the other pairs, and the S and D pairs in deformed nuclei are shown to carry the major fraction of the quadrupole moment.
TL;DR: In this article, counterstreaming large-diameter electron beams in a steady-state laboratory experiment were observed to generate transverse radiation at twice the upper-hybrid frequency (2omega-UH) with a quadrupole radiation pattern.
Abstract: Counterstreaming large-diameter electron beams in a steady-state laboratory experiment are observed to generate transverse radiation at twice the upper-hybrid frequency (2omega-UH) with a quadrupole radiation pattern. The electromagnetic wave power density is nonlinearly enhanced over the power density obtained from a single beam-plasma system. Electromagnetic power density scales exponentially with beam energy and increases with ion mass. Weak turbulence theory can predict similar (but weaker) beam energy scaling but not the high power density, or the predominance of the 2omega-UH radiation peak over the omega-UH peak. Significant noise near the upper-hybrid and ion plasma frequencies is also measured, with normalized electrostatic wave energy density W(ES)/n(e)T(e) approximately 0.01.