Showing papers on "Quadrupole published in 1972"
TL;DR: In this paper, the radiofrequency and microwave spectra of the K = 0 states of (HF)2, (DF)2 and (HFDF) have been studied by the molecular beam electric resonance method.
Abstract: The radiofrequency and microwave spectra of the K=0 states of (HF)2, (DF)2, and HFDF have been studied by the molecular beam electric resonance method. A unique hydrogen tunnelling motion involving the breaking and reforming of the hydrogen bond causes a splitting of rotational energy levels for (HF)2 and (DF)2, but not for HFDF. The electric dipole selection rules and nuclear spin statistics for the tunnelling molecules have been derived from a consideration of an extended permutation‐inversion group. Rotational constants, tunneling doublings, electric dipole moments, and deuterium quadrupole coupling constants have been determined from the observed spectra of the K=0 states. (HF)2(DF)2HFDF(B+C)/2 (MHz)6504.8±2.06252.194±0.0026500.1±0.1ν (MHz)19 776±121579.877 ±0.004μa (D)2.987±0.0032.9919±0.00063.029±0.003(eqQ)Da (KHz)···110±8270±30 These results are interpreted with a semirigid, nonlinear model of the dimer geometry. The F—F distance is 2.79 ± 0.05 A, and the end hydrogen fluoride unit is bent from 60...
515 citations
TL;DR: In this article, the Stockmayer potential was extended to include the term of order μ6, where μ is the dipole moment, and the effects of higher-order terms were then approximated by means of a simple Pade extrapolation procedure.
Abstract: The study of polar fluids begun in a previous paper is continued. Calculations for the Stockmayer potential are extended to include the term of order μ6, where μ is the dipole moment. The effects of higher-order terms are then approximated by means of a simple Pade extrapolation procedure, and the liquid-gas coexistence curve is located in this approximation. An orientation-independent but temperature-dependent potential that is thermodynamically equivalent to an arbitrary orientation-dependent potential is introduced and used to assess the lowest-order thermodynamic effects that result from the presence of quadrupole and octupole terms in the pair-potential. Several values of quadrupole and octupole moments representative of a dipolar molecule (HCl) as well as linear molecules (N2, O2 and CO2, for which μ=0) are considered.
260 citations
TL;DR: The NMR spectra of nitrogen nuclei may provide an important contribution to the development of the general theory of chemical shifts, by allowing a rigorous check of current theories as discussed by the authors.
Abstract: Publisher Summary Nitrogen nuclear magnetic resonance (NMR) is finding new applications. This chapter presents some of the applications of the nitrogen NMR. The element nitrogen in its natural occurrence has two isotopes; 14N and 15N. The nuclei of both possess magnetic moments; consequently, both give nuclear magnetic resonance (NMR) spectra and additionally may affect the spectra of other nuclei. The NMR spectra of nitrogen nuclei may provide an important contribution to the development of the general theory of chemical shifts, by allowing a rigorous check of current theories. This arises from the variety of nitrogen valence states occurring in the molecules, including more or less non-bonding electron pairs, many types of bonds of varying polarity and hydrogen bonding, as well as the common occurrence of nitrogen atoms in both neutral and ionic species. 14N nucleus has an electric quadrupole moment and this is responsible for producing broad-line NMR spectra. Broad lines often occur both in the spectrum of the 14N nucleus and in the spectrum of any nucleus spin coupled to the nitrogen nucleus that may preclude the detection of any spin-spin coupling between these nuclei. The electric quadrupole relaxation process of the 14N nucleus may influence the NMR spectra of nuclei that are spin-coupled to it. The most frequently encountered example is the N-H coupling. The chapter presents some examples of nitrogen chemical shifts in the organic and inorganic molecules. However, spin-spin coupling, involving nitrogen nuclei, is readily observed for the 15N isotope than for 14N. As 15N nuclei possess a spin of 1/2 and no quadrupole moment, these give NMR spectral patterns similar to those arising from lH and 19F interactions.
200 citations
110 citations
TL;DR: In this paper, the excitation of the giant dipole and quadrupole states in nuclei was investigated and two simple models were used for the transition densities and potentials in the dipole excitation.
101 citations
TL;DR: Differential cross sections are measured for the elastic and inelastic scattering of 104 MeV α-particles from 20Ne, 22Ne, 24Mg, 26Mg and 28Si as mentioned in this paper.
99 citations
TL;DR: In this paper, the potential curves and electronic wavefunctions for the states X, 1Σ+, A, 1 Σ+, B 1Π, 3Σ+ and 3Π for LiH, various properties were calculated.
Abstract: Using accurate ab initio calculated potential curves and electronic wavefunctions for the states X 1Σ+, A 1Σ+, B 1Π, 3Σ+, and 3Π for LiH, various properties were calculated. These include dipole and quadrupole moment, field gradient at the nuclei, etc. Rotation‐vibrational wavefunctions were obtained and a rotation‐vibrational analysis was carried out. Some of the properties obtained were averaged over the appropriate rotation‐vibrational wavefunctions. In addition electronic transition moments were computed and from this uv and ir line strengths were obtained. In general the agreement with experimental values, where available, is satisfactory.
88 citations
TL;DR: In this article, a systematic study of inelastic proton continuum spectra produced at small angles by bombardment of 27Al, 54Fe, 120Sn and 209Bi with 62 MeV protons suggests the existence of a collective region in the continuum with properties of a giant quadrupole vibration.
84 citations
TL;DR: In this article, the angle variation of the 93Nb NMR linewidths is obtained for an off-stoichiometry lithium niobate crystal and the widths can be calculated on the basis of a model in which both the magnitude and direction of the electric field gradient are treated as random quantities.
Abstract: The angle variation of the 93Nb NMR linewidths is obtained for an off‐stoichiometry lithium niobate crystal. It is shown that the widths can be calculated on the basis of a model in which both the magnitude and direction of the electric field gradient are treated as random quantities. A second type of niobium, with a near zero quadrupole coupling constant, is shown to exist in off‐stoichiometric crystals. This amounts to roughly 6% of the total niobiums. This new resonance is undoubtedly associated with the mechanism of charge compensation and suggests that the excess niobium substitutes for lithium.
83 citations
77 citations
TL;DR: The molecular transient methyleneimine (CH2=NH) has been identified in the gas phase from its microwave spectrum as mentioned in this paper, and the half-life of this transient molecule is estimated to be less than 0.1 sec under the conditions used in the experiment under discussion.
TL;DR: In this article, it is shown that the partial field gradient associated with a given ligand is different for tetrahedral, trigonal-bipyramidal-apical, triconnective-equatorial, and octahedral co-ordination positions.
Abstract: Mossbauer quadrupole splitting in organotin(IV) compounds is interpreted in terms of the additive approximation, in which the total electric field gradient at the 119Sn nucleus is written as a sum of partial field gradient tensors. Localized orbitals are shown to provide the natural framework for discussion of additive electric field gradients, and it is conjectured that the existence of a suitable localization transformation is a necessary condition for additivity. It is shown that the partial field gradient associated with a given ligand is different for tetrahedral, trigonal-bipyramidal-apical, trigonal-bipyramidal-equatorial, and octahedral co-ordination positions. In particular, the partial field gradient for octahedral co-ordination is about 70%(experiment indicates 75%) of that for tetrahedral. Absolute numerical values for partial field gradient parameters cannot be obtained from experiment for any of the above co-ordination positions, but the evaluation of relative parameters is discussed, and working values are given for a variety of ligands in tetrahedral or octahedral structures. Quadrupole splittings calculated by use of these values agree with observed splittings to within 0·4 mm s–1 or better. Alternatively, disagreement may be used as evidence of large distortions or incorrect assignment of structure. It is shown that a literal'point-charge' treatment of the effect of distortions from idealized geometry cannot be justified in molecular-orbital terms. Illustrative calculations are performed for tetrahedral systems, but experimental data indicates that it is better to ignore small distortions in quantitative discussion of the magnitude of quadrupole splitting. Extension of the model to octahedral complexes of low-spin Fe(II) is briefly discussed.
TL;DR: The equivalent heart dipole and quadrupole were determined on a normal male subject for two origins in the heart region based on a detailed measurement of the torso surface geometry, a digital computer solution of transfer impedances relating unit dipoles and Quadrupole components to surface potentials they generate, and the measurement of 284 ECG's.
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TL;DR: In this article, the rotational and quadrupole coupling constants of I35Cl and I37Cl were obtained and the iodine nuclear spin-rotation constant was determined by Stark effect measurements.
Abstract: The J = 2 ← 1 microwave spectra of I35Cl and I37Cl are measured for the v=0 and v=1 vibrational levels. The dipole moment μ (v = 0) = 1.24 ± 0.02 D is determined by Stark effect measurements. Improved values of the rotational and quadrupole coupling constants are obtained and the iodine nuclear spin—rotation constant is determined.
TL;DR: In this article, the reorientation effect in Coulomb excitation was used to measure the static electric quadrupole moments of the first excited (2+) states in 48Ti and 56Fe.
TL;DR: In this paper, the average absolute deviation between the calculated and experimental binding and excitation energies is 0.11 MeV (with the exclusion of 66 Ni), while the average measured strengths are 7.0 and 0.07 W.u., respectively.
TL;DR: In this paper, the ground vibronic Stark coefficient and the nuclear quadrupole coupling constants eqQ were obtained for the |MJ|=0→ 1 transition in the J = 1, v=0 state in a supersonic beam.
Abstract: Molecular beam electric resonance spectra for several heteronuclear alkali dimers have been obtained for the |MJ|=0→ 1 transition in the J = 1, v=0 state in a supersonic beam. Values of the ground vibronic Stark coefficient μ02/B0 and the nuclear quadrupole coupling constants eqQ were obtained. The values of μ02/B0 were (2.269± 0.002)× 10−19 cm3 for 39K7Li, (3.697± 0.004)× 10−19 cm3 for 85Rb7Li, and (3.966± 0.004)× 10−18 cm3 for 39K23Na. Badger's rule was used to estimate B0 and to determine the following values for the molecular electric dipole moment: μ0(39K7Li)=3.45± 0.1 D, μ0(85Rb7Li)=4.00± 0.1 D, and μ0(39K23Na)=2.76± 0.1 D, where the errors arise from the uncertainties in the rotational constant. Electric deflection was used to obtain a value of μ2/B for Rb23Na of (6.6± 0.5) × 10−19 cm3 and hence 3.1± 0.3 D for the dipole moment, while rf spectroscopy with power broadening was employed with 133Cs23Na to obtain (1.81± 0.02) × 10−18 cm3 for μ02/B0 and hence 4.75± 0.2 D for μ0. The translational and rotational temperatures in the supersonic beams were estimated from velocity scans and quadrupole voltage scans. An ionic model is used in a heuristic interpretation of the dipole moment results.
TL;DR: In this article, the authors derived the electric quadrupole moment of the indium-cadmium alloy (0.94 at.% indium) for the stable indium isotopes in the same environment using the nuclear-quadrupole resonance (NQR) technique.
Abstract: The quadrupole interactions of the 247-keV state of $^{111}\mathrm{Cd}$ populated in the decay of $^{111}\mathrm{In}$ have been studied by time-dependent perturbed-angular-correlation measurements in environments of metallic indium and indium-cadmium alloys. Periodic undamped-spin-rotation curves were observed which prove that in both cases the axial-asymmetry parameter of the electric field gradient is close to zero and the spread of the interaction frequencies is negligibly small. The temperature dependence of the interaction frequencies in metallic indium is quite strong but deviates only slightly from that observed by Hewitt and Taylor for the stable indium isotopes in the same environment using the nuclear-quadrupole-resonance (NQR) technique. We draw the conclusion that the localized-moment contribution of the conduction electrons to the electric field gradient must be small in this case, and by using the results of Hewitt and Taylor for a calibration of the effective electric field gradient, we derived for the electric quadrupole moment of the 247-keV state of $^{111}\mathrm{Cd}$ ${Q}_{\frac{5}{2}}=+0.44\ifmmode\pm\else\textpm\fi{}0.07\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}24}$ ${\mathrm{cm}}^{2}$. The quadrupole interactions in the indium-cadmium alloy (0.94 at.% indium) were found to be an order of magnitude larger than in indium. This was expected because of the anomalously large $\frac{c}{a}$ crystal-axes ratio of the hexagonal-close-packed (hcp) lattice of cadmium. The observed temperature dependence gives interesting information about the role of the conduction electrons as well as about the phase diagram of the cadmium-indium system.
TL;DR: In this paper, a sensitive nuclear double resonance method enables measurement of naturally abundant 17 O nuclear quadrupole resonance transition frequencies in powdered organic compounds, enabling the identification of resonances from C�O, CO-C groups in a set of compounds.
TL;DR: In this paper, the potential of mean force between two impurities in a sample of a fluid of rigid dipoles is studied and the longest-range part of the potential obtained from a molecular theory is the same as the interaction energy obtained from macroscopic electrostatics, when the polar fluid is treated as a dielectric continuum.
Abstract: The potential of mean force between two impurities in a sample of a fluid of rigid dipoles is studied. Each impurity may be a charge, an electric dipole or an electric quadrupole. It is found that the longest‐range part of the potential of mean force obtained from a molecular theory is the same as the interaction energy obtained from macroscopic electrostatics, when the polar fluid is treated as a dielectric continuum, except that the impurity dipole and quadrupole have to be replaced by effective dipole moments. These effective dipole moments arise because of the local polarization of the polar molecules in the surrounding of the impurities, due to the local interactions. Next a pure polar fluid in the presence of an arbitrary external electric field is considered. The one‐particle distribution function in the presence of the field is studied to all orders in the field. It is found that both this one‐particle distribution function and the dielectric polarization are shape‐independent functions of the local average macroscopic field.
TL;DR: In this paper, the quadrupole (ϵ2)- octupole potential energy surface for nuclei beyond 208Pb indicates the presence of a very low lying secondary minimum in the oblate octupoles region of deformation for certain nuclei.
TL;DR: In this paper, the Anderson-Tsao-Curnutte's theory of collision broadening has been applied to the asymmetric-top molecules and theoretical formulations of broadening due to dipole-dipole, dipole quadrupole, quadrapole-duplicate quadrupoles, quadruphole-dipsole, debye induction force interactions are developed.
Abstract: The Anderson-Tsao-Curnutte's theory (1.2) of collision broadening has been applied to the asymmetric-top molecules. Theoretical formulations of broadening due to dipole-dipole, dipole-quadrupole, quadrupole-dipole, quadrupole-quadrupole and Debye induction force interactions are developed. Asymmetry of the electric charge distribution was taken into account in considering the quadrupole moment of the asymmetric-top molecule. It is shown that the shape of the electric-charge distribution affects the value of the line width when the quadrupole moment is large.
TL;DR: The pure quadrupole resonance of 17 O has been detected in enriched ice at 77°K as mentioned in this paper, where the coupling constants obtained are very different from those of the isolated molecule indicating the powerful role played by hydrogen bonding in the solid.
TL;DR: In this paper, the molecular Zeeman effect in the following strongly nuclear coupled molecules was analyzed in magnetic fields near 20 000 G: 35ClF, 37ClF and 79BrF, 81BrF and 35Cl12C15N.
Abstract: The molecular Zeeman effect in the following strongly nuclear coupled molecules was analyzed in magnetic fields near 20 000 G: 35ClF, 37ClF, 79BrF, 81BrF, 35Cl12C15N, 37Cl12C15N, 79Br12C15N, 81Br12C15N, and 127I12C15N. The molecular g values, the shielded nuclear g values, magnetic‐susceptibility anisotropies, and molecular quadrupole moments are determined for each of the above molecules. The isotope dependence in the molecular g values gives the electric dipole‐moment sign in −ClF+ and +ClCN−. The 127I nuclear magnetic shielding anisotropy in 127I12C15N was also determined. The known molecular structures combined with the above Zeeman data were used to determine the paramagnetic‐ and diamagnetic‐susceptibility tensor elements.
TL;DR: In this paper, Hartree-Fock calculations have been performed in light 4 n nuclei from 8 Be to 28 Si using central interactions, and the rms radii, static quadrupole moments and electromagnetic transition rates have been deduced exactly from the angular momentum projected wave functions obtained in a projection before variation (PBV) procedure.
TL;DR: Admixtures of one-and two-phonon states are required to fit (e, e′) form factors for the lowest two 2 + states in several even-even vibrational nuclei.
Patent•
20 Nov 1972
TL;DR: In this paper, a method for the detection of the natural magnetic and/or electric quadrupole reasonance frequencies of isotopically rare or chemically dilute nuclei in the presence of at least one abundant nuclear spin species is described.
Abstract: A method is described for the detection of the natural magnetic and/or electric quadrupole reasonance frequencies of isotopically rare or chemically dilute nuclei in the presence of at least one abundant nuclear spin species. The free induction decay of the dilute nuclei is directly detected after an applied r.f. field at the Larmor frequency of the dilute nuclei is removed. A high resolution spectrum of the dilute nuclei is obtained by applying an r.f. field at the Larmor frequency of the abundant spin system during the detection interval.
TL;DR: In this article, the monopole and quadrupole pairing residual interactions acting simultaneously on a system of particles which move in a set of Nilsson single-particle levels and display a nonuniform distribution of positive and negative quadrupoles moments around the Fermi surface give rise to BCS state dependent gaps, which can produce effects which are similar to those appearing when there is an energy gap in the singleparticle spectrum.