Showing papers on "Quadrupole published in 1977"
TL;DR: In this paper, the double nuclear resonance techniques have been used for the detection of the nuclear quadrupole resonance (N.Q.R.) of many light elements which would have been impossible only a few years ago using conventional techniques.
215 citations
201 citations
TL;DR: In this article, the molecular-beam electric-resonance method was used to investigate the Stark-Zeeman spectra of the J = 1, v = 0 state of CO. The experimental results were used to determine the polarity of the electronic charge distribution, the vibrational dpendence of the electric dipole moment, and the molecular quadrupole moment.
142 citations
133 citations
TL;DR: In this paper, a vibrating potential model is applied to deformed nuclei with a deformed harmonic oscillator potential in order to discuss the splitting of isoscalar giant quadrupole states.
125 citations
TL;DR: In this paper, the action of light in a transparent medium is studied by Mossbauer resonance and a new kind of molecular state, producable only by polarized light, was observed.
Abstract: In a “crossed photon beams” experiment the action of light in a transparent medium is studied by Mossbauer resonance. Using cooled, temperature stabilized targets such as sodium nitroprusside, olivine and glasses, containing iron, no change of the hyperfine spectrum was observed by illumination with normal incoherent light of low intensity within the region of normal dispersion in agreement with the theory of optical dispersion. There was, however, no agreement with theoretical expectation when sodium nitroprusside (whose structure is, therefore, reviewed in detail under the aspects of dispersion) was irradiated by laser light with otherwise unchanged experimental conditions, as intensity and range of wavelengths. A new kind of molecular state, producable only by polarized light, was observed. Its radiative lifetime is practically infinite, but it is thermally instable at elevated temperatures. The Mossbauer spectrum reveals a quadrupole splittingΔE
Q= (+)(2.7357±0.0040)mm/s and an isomer shiftδ=}-(0.183±0.006)mm/s (relativ to Fe(Pd)) at 100 K, markedly different from the normal groundstate. In the new state the axial symmetry, the sign of thez-component, and the three principal tensor axes of the electric field gradient at the Fe central atom coincide within the experimental limits of error with those of the groundstate.
115 citations
TL;DR: In this paper, the molecular dynamics method has been used to study a model system of 256 homonuclear diatomic molecules governed by intermolecular potentials of the form U = UAA + Z7QQ, where UAA is an atom-atom potential and C/QQ is the quadrupole-quadrupole potential.
Abstract: The molecular dynamics method has been used to study a model system of 256 homonuclear diatomic molecules governed by intermolecular potentials of the form U = UAA + Z7QQ, where UAA is an atom-atom potential and C/QQ is the quadrupole-quadrupole potential. For UAA both the full Lennard-Jones and the repulsive part only of the Lennard-Jones potential have been used, and C7QQ has been used with reduced quadrupole moments, Q* = $/(e L* = L/cr (bond length/atom diameter) between 0.33 and 0.63 have been studied, at reduced temperatures * =kT/e from 0.98 to 3.48 and reduced densities p* = pal from 0.522 to 1.043 (where ae is the diameter of a sphere having a volume equal to that of the diatomic). Detailed orientational structure in the liquid has been examined by calculating as many as 22 terms in the spherical harmonic expansion of the angle dependent pair distribution function. At short distances these systems exhibit a high degree of angular correlation, which increases with increasing elongation and density. Pair correlation functions calculated from the Lennard-Jones and Lennard-Jones repulsive models are virtually identical, other parameters being equal, and are similar to those for hard diatomics, indicating that both radial and orientational structure are determined mainly by short-range repulsive forces. The addition of a moderately strong quadrupole term to the potential produces dramatic changes in structure and significant changes in thermodynamic properties. A potential with a moderately strong quadrupole term is found to give the correct qualitative features for the structure factor of liquid bromine.
110 citations
01 Mar 1977
TL;DR: The 57Fe Mossbauer effect of solvated tris(2-aminomethylpyridine) iron (II) chloride has been studied in detail between 80 and 310 K as discussed by the authors.
Abstract: The 57Fe Mossbauer effect of solvated tris(2-aminomethylpyridine) iron (II) chloride has been studied in detail between 80 and 310 K. The methanolate exhibits a gradual but complete spin transition between 1A1 and 5T2. At 153 K, both the intensities of 1A1 and 5T2 quadrupole doublets become equal. An extremely large hysteresis (ΔT = 91 K) has been observed for the cooperative 1A1 ⇌5T2 transition in the monohydrate. The critical transition temperature is TC = 295 K for the heating and TC = 204 K for the cooling direction. The spin state of the dihydrate is the low-spin 1A1 state over the whole temperature range studied. A remarkable influence of the non-coordinating solvent molecule on the spin transition behaviour (e.g., TC the quadrupole splitting, cooperative effect) has been found in the present series of complexes. This is accounted for in terms of a combined action of both the hyrdrogen-bond formation between the ligand and the intervening solvent molecule and a change in the relevant phonon system caused by different packing geometry and/or possible crystallographic change. A ligand-field calculation indicates an orbitally non-degenerate 5A1 or a 5A2 ground state under a trigonal or a rhombic distortion in the high-spin state.
108 citations
TL;DR: In this article, the dipolar broadening of the magnetic field sensed by an interstitial impurity in a rigid lattice is calculated with the electric-field gradient set up by the impurity taken into account.
Abstract: The dipolar broadening of the magnetic field sensed by an interstitial impurity in a rigid lattice is calculated with the electric-field gradient set up by the impurity taken into account. This is shown to give a strong dependence of the dipolar width on the applied magnetic field. The theory is especially applicable to the linewidth of precessing muons in metals.
106 citations
TL;DR: In this paper, it was shown that the temperature variation of the magnetic fields at the two non-equivalent B-sites is proportional to the sublattice magnetization, suggesting that the deviations arise from a variation in band overlap.
Abstract: Mossbauer spectroscopic studies (57Fe) of powdered magnetite have been undertaken between 120 K and 880 K. Below the magnetic transition temperature (T
C=839.5 K) three six-line patterns have been fitted to our experimental spectra. The broadening of the B-pattern is explained by two magnetically non-equivalent B-site irons, suggesting broadening due to electron hopping to be negligible. In the paramagnetic state the electric quadrupole splittings of iron at A-and B-sites are found to be constant, independent of temperature, having the values zero and 0.16 mm/s, respectively. The centroid shifts, on the other hand, show above 700 K large deviations from the calculated second order Doppler shift. It is proposed that the deviations arise from a variation in band overlap. The temperature variation of the magnetic fields is found to be proportional to the sublattice magnetization. The difference in the magnetic fields at the two non-equivalent B-sites is measured to be 1.1 T at 310 K.
104 citations
TL;DR: In this paper, the theory of X-ray scattering and the derivation of electron densities from X-Ray scattering amplitudes are discussed, and the comparison of theoretical and experimental densities is discussed.
Abstract: Publisher Summary This chapter discusses the theory of X-ray scattering and provides the derivation of electron densities from X-Ray scattering amplitudes. Even though X-ray diffraction is conventionally used for the determination of atomic positions, the X-ray scattering amplitudes depends directly on the electronic wavefunction, from which atomic positions can only be derived under the assumption of coincidence of the nuclear positions and the centroids of electronic charge. The comparison of theoretical and experimental densities is discussed, and the functions based on experimental densities are reviewed. In addition to Fourier methods, least-squares fitting of density functions may be accomplished directly in scattering space analogous to least-squares adjustment of atomic parameters in conventional crystallography. The chapter briefly mentions the valence shell deformation methods. The space-filling properties of formalisms, including atomic dipole, quadrupole, octopole, and hexadecapole terms may be judged from the molecular density maps based on the multipole expansion coefficient.
TL;DR: In this paper, the effect of the choice of the potential function on the evaluation of molecular multipole moments from pressure-induced far-infrared spectra is investigated, restricted to low densities where collisions are predominantly bimolecular.
Abstract: The effect of the choice of the potential function on the evaluation of molecular multipole moments from pressure‐induced far‐infrared spectra is investigated. The analysis is restricted to low densities where collisions are predominantly bimolecular. The quadrupole and hexadecapole moments of N2 and O2, and the octupole and hexadecapole moments of CH4 and CF4 are evaluated from far‐infrared data using potential models consisting of a spherically symmetric part represented by the Lennard‐Jones, Kihara, and m–6–8 potentials and an anisotropic part representing the electrostatic interactions of the permanent multipole moments. In general, although different values of the multipole moments are obtained with different potentials, for similar molecular diameters the variation is not great.
TL;DR: The use of a radio-frequency ion trap having cylindrical geometry is considered in this article, where theoretical aspects of such a device are given in detail; some experimental studies and a numerical examination are discussed briefly.
TL;DR: In this paper, a model for the magnetospheric magnetic field of Mercury is presented, where the external field is represented by an image dipole and a tail field and the internal field includes a dipole, a quadrupole, and an octupole.
Abstract: This paper presents a model for the magnetospheric magnetic field of Mercury in which the external field is represented by an image dipole and a tail field and the internal field includes a dipole, a quadrupole, and an octupole. The dipole moment estimated by this model is approximately 2.4 x 10 to the 22nd G cu cm, tilted 2.3 degrees from the normal to the planetary orbital plane and having the same directional sense as that of the earth. The dipole, quadrupole, and octupole moment intensities are in the approximate ratios 1:0.4:0.3, respectively. All planetary field lines of the model magnetosphere are confined to a magnetospherelike region. Results are obtained which show the geometry, field line configuration, and field isointensity contours inside the magnetosphere of Mercury.
TL;DR: In this article, the Stark and Zeeman transitions within single J states of ozone have been studied using molecular beam electric resonance spectroscopy, and the results include dipole moments, μ; dipole moment of the first excited bending mode, μ (010); polarizability anisotropies, αaa−αbb and αAA−αcc; rotational magnetic moments, ga, gb, gc; magnetic susceptibility anisotropic, χaa−χbb and χAA−φcc; and quadrupole moment components, �
Abstract: Stark and Stark–Zeeman transitions within single J states of ozone have been studied using molecular beam electric resonance spectroscopy. Results include dipole moment, μ; dipole moment of the first excited bending mode, μ (010); polarizability anisotropies, αaa−αbb and αaa−αcc; rotational magnetic moments, ga, gb, gc; magnetic susceptibility anisotropies, χaa−χbb and χaa−χcc; and quadrupole moment components, ϑaa, ϑbb, ϑcc. μ=0.5337(1) D, μ (010) =0.5261(1) D, αaa−αbb=2.82(1) A3, αaa−αcc=2.63(4) A3, gaa=2.98933(8), gbb=−0.22919(3), gcc=−0.07623(b), χaa−χbb=5.91(2) KHz/kg2, χaa −χcc=12.05(4) KHz/kg2, ϑaa=−1.4(2) ×10−26 esu⋅cm2, ϑbb=−0.7(2) ×10−26 esu⋅cm2, ϑcc=2.1(3) ×10−26 esu⋅cm2.
TL;DR: The interpretation of the NMR spectra of membrane systems poses problems but at the same time there is a lot of information to be gained.
Abstract: There is an inherent anisotropy in biological and model membrane systems and this anisotropy has a profound influence on the nuclear magnetic resonance spectra of such systems. For nuclei with a quadrupole moment the quadrupole coupling usually dominates the NMR spectrum, while for nuclei with spin quantum number I = ½ dipolar couplings provides the most important effects. The quadrupole coupling only affects isolated spins and usually gives rise to simple spectra. The dipole interactions on the other hand couple several spins. In a lipid bilayer with a multitude of spin-½ nuclei these couplings can give rise to complicated manybody effects. Thus the interpretation of the NMR spectra of membrane systems poses problems but at the same time there is a lot of information to be gained.
TL;DR: In this article, the optimum operating point of the trap and the average ion energy were determined in preparation of an ODR experiment to determine the ground state hyperfine splitting of the odd isotopes.
Abstract: The observation of D1-fluorescence light from trapped Ba+ ions, using a pulsed tunable dye laser as a light source, leads to a sensitive detection of the confined particles. In preparation of an ODR-experiment to determine the ground state hyperfine splitting of the odd isotopes we found the optimum operating point of the trap and measured the average ion energy.
Abstract: According to the spin-coupled theory of structure of molecules, the wavefunction is constructed from configurations of non-orthogonal orbitals whose spins are coupled to the required overall resultant in all allowable ways (Gerratt 1971). This approach is here applied to the molecules LiH, BH, Li 2 and HF. Two cases are considered: (i) a single configuration of non-orthogonal orbitals and (ii) a linear combination of two such configurations. The resulting wavefunctions are used to calculate theoretical values for a series of molecular properties including binding energy, equilibrium internuclear distance, force constant, dipole (or quadrupole) moment, dipole (or quadrupole) moment derivative, electric field gradient at a nucleus and net force on a nucleus. The values of these properties, particularly in case (ii), are all in excellent agreement with experiment. Notably, the calculated values of binding energies are 90-96 % of observed, except for Li 2 where the corresponding percentage is 80. The quality of these wavefunctions is considerably better than many-structure v.b. functions, and comparable with very large m.o.-c.i. or m.c.s.c.f. wave functions. The implementation of this approach involves the use of highly efficient methods for calculating the necessary n -electron density matrices, and for optimizing the orbital and spin-coupling coefficients. These techniques are fully described.
TL;DR: In this article, it was shown that in the limit of perfect data and an infinite Ewald sphere, a least-squares fit with a many-centered finite multipole expansion of the charge density about the N nuclei will necessarily satisfy the q-centered multipoles of the molecule for q = 1, 2,…, N. This means that a large number of static charge physical properties (averages over ρ(r)) are correctly given.
Abstract: The one-electron density function, ρ(r), (in principle deduced from elastically scattered X-ray intensities) is the probability distribution function of an electron, averaged over the positions of all other electrons. A partitioning of ρ(r) into constituent parts is an intellectual exercise that does not lend itself to unique measurement from elastic X-ray scattering experiments. It is shown that in the limit of perfect data and an infinite Ewald sphere, a least-squares fit with a many-centered finite multipole expansion of the charge density about the N nuclei will necessarily satisfy the q-centered multipoles of the molecule for q = 1, 2,…, N. This means that a large number of static-charge physical properties (averages over ρ(r)) are correctly given. Several expressions for averages of ρ(r) or over FH are given. It is shown that outer moments, such as atomic charges, dipole moments and quadrupole moments, always depend on a shape function. On the other hand, inner moments such as potentials, electric forces, and electric field gradients, may be represented by direct Fourier analysis of FH (obs) (suitably phased, of course). Nuclear vibrations have been neglected throughout the discussion.
TL;DR: In this article, the nuclear quadrupole hyperfine splittings of Pr3+ in LaF3 have been measured for the ground electronic state using a RF optical resonance technique, and a hamiltonian H = P[(I2z− 13I(I+1) + (η/6)(I2+−I2-)] was fitted to the data with zP=4.185 ± 0.003 MHz and η = 0.105 ± 0010.
TL;DR: In this paper, a method for the calculation of the strength function photoexcitation of giant multipole resonances in spherical nuclei is presented, based on the quasiparticle-phonon interaction.
TL;DR: In this paper, the quadrupole moment of the 8-mu..s fission isomer in /sup 239/Pu has been determined with a newly developed charge-plunger technique for measuring lifetimes of states decaying by converted transitions.
Abstract: The quadrupole moment of the 8-..mu..s fission isomer in /sup 239/Pu has been determined with a newly developed charge-plunger technique for measuring lifetimes of states decaying by converted transitions. With a statistical accuracy of 7%, values between 34 and 39 b are obtained, depending on the unknown isomeric spin. The deformation of the second minimum described by the axis ratio of a spheroid is deduced to be c/a=2.0 +- 0.1.
TL;DR: In this paper, the effects of coupling between the field gradient excited by the charge perturbation and the quadrupole moments of (host) nuclei on the nuclear magnetic resonance (N.M.R.) signal are summarized and various kinds of experiment based on this quadrupoles effect are discussed.
Abstract: The calculated properties of the charge perturbations around impurities in metals are summarized and contrasted with the experimental situation in this field. The effects of coupling between the field gradient excited by the charge perturbation and the quadrupole moments of (host) nuclei on the nuclear magnetic resonance (N.M.R.) signal are summarized and various kinds of experiment based on this quadrupole effect are discussed. The gross overall features of the charge perturbation are established by analysing N.M.R. data for copper and aluminium based alloys. This analysis leads to the conclusion that simple theories can account for the main experimental findings, but details, in particular the anisotropy of the charge perturbation, cannot be fully explained because band structure effects play an important role. The relevance of phase-shift analysis is also assessed, and its applicability in cases of complicated Fermi surfaces is discussed. Effects connected with the energy dependence of the sca...
TL;DR: In this article, the reorientation effect in Coulomb excitation was employed to measure the static quadrupole moments of the first 2 + excited states in 76 Se, 78 Se, 80 Se, and 82 Se.
TL;DR: In this article, the first measurements of deuterium quadrupole coupling constants of a polyatomic doublet state radical were reported, which were determined by endor and electron-nuclear-nuclear TRIPLE resonance in liquid crystals.
Abstract: First measurements of deuterium quadrupole coupling constants of a polyatomic doublet state radical are reported. The quadrupole couplings were determined by ENDOR and electron–nuclear–nuclear TRIPLE resonance in liquid crystals. For the partially deuterated perinaphthenyl radical the out‐of‐plane component of the deuterium quadrupole coupling was measured to be e2q33Q/h =−(94±3) kHz for both molecular sites. Within experimental error these values are equal to those measured earlier for deuterated alternant hydrocarbons in the diamagnetic singlet ground state.
TL;DR: In this article, it is shown that the angular dependence of the self-decoupling is not due to differences in the static 1H-127I dipolar coupling, but reflects the angular variation of the 127I relaxation rates.
TL;DR: In this article, the transient pulsed response of an ensemble of nuclei with spin I = 3/2 experiencing electric quadrupole couplings is calculated, both in zero field and in the presence of a weak, applied static field.
Abstract: Using the interaction representation, the transient pulsed response of an ensemble of nuclei with spin I=3/2 experiencing electric quadrupole couplings is calculated, both in zero field and in the presence of a weak, applied static field. It is found that, in this representation, the evolution of the density operator depends, to a good approximation, on a time-independent effective hamiltonian. For the response to a solitary, resonant 90° pulse, the prediction is made of the existence of two transient decay signals, 90° out of phase with each other, one being determined by the even moments of the absorption line (as in the ordinary N.M.R. case) and the other being determined by the odd moments. This second signal will be present in the N.Q.R. case, since here the effect of dipole-dipole couplings seems to be, in general, to broaden the resonance line at ω0 asymmetrically, and while the first moment can be proved to be always zero, this is not, in general, true of the higher odd moments. Expressions are de...
TL;DR: In this article, it was shown that high-spin states formed by adding a few valence nucleons to /sup 208/Pb can be accurately calculated by using empirical interaction matrix elements.
Abstract: The energies of high-spin states formed by adding a few valence nucleons to /sup 208/Pb can be accurately calculated by using empirical interaction matrix elements. It is shown that the energies of high-spin states with /sup 207/Pb, /sup 206/Pb, and /sup 204/Pb as the core can also be accurately calculated if an additional quadrupole interaction with a strength proportional to the increased polarizability of the core is included. This interaction may contribute to the formation of yrast traps from states with a few valence nucleons with aligned angular momenta.
TL;DR: The nuclear quadrupole couplings of NH4ReO4 have been measured over a wide range of temperatures, showing that disappearance of the resonance is due to gradients of temperature and strain in the sample.
Abstract: The nuclear quadrupole couplings of the 187Re, 14N, and 2H nuclei in NH4ReO4 have been measured over a wide range of temperatures. The 187Re nuclear quadrupole resonance has been observed throughout the previously reported ’’wipeout’’ range of temperature, showing that disappearance of the resonance is due to gradients of temperature and strain in the sample. The pressure dependence of 187Re quadrupole resonance has been measured as a function of temperature between 77 and 362 K. The slope of the graph of (∂ν/∂P)T versus temperature is indicative of a continuous phase transition at this temperature. The nature of the phase transition and its relationship to other phenomena in NH4ReO4 is unclear.
TL;DR: In this article, it was shown that the effective potential for electron-atom scattering, below inelastic thresholds, has the asymptotic form - alpha r-4-( alpha q-6 beta -24 gamma k12)r-6- delta r-7+O(r-8).
Abstract: It is shown that the effective potential for electron-atom scattering, below inelastic thresholds, has the asymptotic form - alpha r-4-( alpha q-6 beta -24 gamma k12)r-6- delta r-7+O(r-8). The expressions for alpha , alpha 1 and beta are well known. The main new result is that the non-adiabatic correction to the dipole polarisation potential is a linear function of k12, namely (6 beta +24 gamma k12)r-6. An exact expression is obtained for gamma . For e-H scattering, gamma =319/48. The term - delta r-7 arises from the fact that the dipole-polarised states have permanent quadrupole moments. For e-H scattering, delta approximately=48.