Showing papers on "Quadrupole published in 1980"
TL;DR: In this article, the Jeener-Broekaert pulse sequence was used to detect deuteron line shapes, from which the orientational distribution of partially ordered solids or solid polymers may be determined.
Abstract: Deuteron spin alignment offers a new possibility to investigate extremely slow rotational motions in solids and solid polymers. A convenient theoretical description of the creation and detection of spin alignment by application of the Jeener–Broekaert pulse sequence is given for both static and slowly time dependent quadrupole coupling, as well as for spin–lattice relaxation of spin alignment. It is shown that the NMR signal following spin alignment yields a correlation function of the time dependent quadrupole coupling. This correlation function is evaluated explicitly for a deuteron on the corner of a regular tetrahedron undergoing tetrahedral jumps. Various applications of deuteron spin alignment are demonstrated experimentally, e.g., its use to obtain undistorted deuteron line shapes, from which the orientational distribution of partially ordered solids or solid polymers may be determined. In solid polyethylene it is shown that not only the deuterons in the crystalline regions but those in the mobile ...
274 citations
TL;DR: In this paper, the relationship between parameters characterizing the proton chemical shift tensors and deuterium quadrupole coupling constants (e2qQ/h) was investigated.
Abstract: Correlations between parameters characterizing the proton chemical shift tensors for O–H⋅⋅⋅O bonded protons in solids and O⋅⋅⋅O hydrogen bond distances and deuterium quadrupole coupling constants (e2qQ/h) are presented. The isotropic value of the chemical shift correlates very well with both RO⋅⋅⋅O and e2qQ/h, whereas the correlations involving the chemical shift anisotropy show much more scatter. A quantitative agreement is found with theoretical calculations performed by Ditchfield.
252 citations
TL;DR: In this article, the collective quadrupole states of the Xe, Ba and Ce isotopes were calculated in the framework of the proton-neutron interacting boson model.
190 citations
TL;DR: In this article, the electric field-gradient birefringence method for determining molecular quadrupole moments, originally developed and applied to gases by Buckingham, has been extended to the study of nondipolar molecules in solution.
Abstract: The electric field-gradient birefringence method for determining molecular quadrupole moments, originally developed and applied to gases by Buckingham, has been extended to the study of nondipolar molecules in solution. Equipment developed for this purpose is described and infinite-dilution molar field-gradient birefringence constants at 298 K and 632.8 nm are reported for benzene, 1,3,5-trimethylbenzene, hexamethylbenzene, 1,3,5-trifluorobenzene and hexafluorobenzene as solutes in carbon tetrachloride. Analysis of results yields the molecular quadrupole moments, which are discussed in relation to the charge distributions in these molecules. The prediction that the quadrupole moments of benzene and hexafluorobenzene are opposite in sign is verified and the nature of molecular interactions involving these molecules is considered.
125 citations
TL;DR: In this paper, the authors used tensorial techniques with particular reference to octahedral complexes to calculate the contribution of vibronic lines in the absorption spectra of rare earth or actinide ions to the neighboring ligands.
Abstract: The intensities of certain lines in the absorption spectra of rare-earth or actinide ions are very sensitive to the neighboring ligands. The contributions to these intensities coming from vibronic transitions (combined electronic and vibrational transitions) are calculated by tensorial techniques with particular reference to octahedral complexes. The expansions that are used possess leading terms that indicate that the strongest vibronic lines should be associated with electronic transitions that satisfy the selection rules on J (the total angular momentum) that are identical to those for quadrupole radiation. General agreement is obtained with the recent work of Faulkner and Richardson on the transition 7F0 → 5D2 of Eu3+, though some of the approximations and assumptions, as well as much of the mathematics, are different.
104 citations
TL;DR: In this paper, a new electron gas intermolecular NH3-He potential determined by the Hartree-Fock results of Davis, Boggs, and Mehrotra with semi-empirical long-range induction and dispersion terms was presented.
Abstract: The paper presents a new electron gas intermolecular NH3-He potential determined by the Hartree-Fock results of Davis, Boggs, and Mehrotra (1979) with semiempirical long-range induction and dispersion terms. The resulting potential agrees with beam scattering and pressure broadening measurements; it was also found that the quadrupole induced dipole interaction is not as effective as the short range anisotropy. It was concluded that discrepancies remain in the quantitative description of energy transfer in the NH3-He system; discrepancies result from improper consideration of the dependence of cross-sections on degenerate magnetic quantum levels in the experimental investigation.
88 citations
TL;DR: In this paper, the rotational spectra have been observed for four isotopes of ArHBr and ArDBr and eight isotopes (ArHBr, DBr and KrHBr) using a Fabry-Perot Fourier transform spectrometer with a pulsed supersonic nozzle as the molecular source.
Abstract: Rotational spectra have been observed for four isotopes of ArHBr and ArDBr and eight isotopes of KrHBr and KrDBr using a Fabry–Perot Fourier transform spectrometer with a pulsed supersonic nozzle as the molecular source. The rotational constants in the ground vibrational state ?0 with their centrifugal distortions DJ, as well as Br nuclear quadrupole coupling constants χa, are given. In addition, an important centrifugal distortion of the Br quadrupole coupling constant, Dχ, an indicator of the coupling between the radial and angular potentials, is given for ArHBr and KrHBr. The Br spin–rotation interaction c in ArHBr is also obtained. The results are: The molecular structures are consistent with a linear equilibrium geometry with the H(D) atom located between Br and the rare gas atoms. The complexes undergo large amplitude vibrations and estimates of the bending and stretching force constants and frequencies are given. By combining the bending, stretching, and their coupling, we have obtained the harmoni...
84 citations
TL;DR: In this article, the local symmetry of amorphous alloys was determined through NMR investigation of quadrupolar effects in some amorphized alloys (La75Ga25, Mo70B30, Mo48Ru32B20, Ni78P14B8).
Abstract: Through NMR investigation of quadrupolar effects in some amorphous alloys (La75Ga25, Mo70B30, Mo48Ru32B20, Ni78P14B8) the local symmetry is determined around the s-p element sites. A comparison with the corresponding crystalline compounds (La3Ga, Mo2B, Ni3B) which have typically different crystal structures (cubic, tetragonal, orthorhombic, respectively) gives conclusive evidence that the amorphous structure retains to a significant extent the local symmetry of the crystalline counterpart.
84 citations
TL;DR: The spatial anisotropy of motion and the segmental fluctuations of the negatively charged phosphoglycerol are similar to those of the zwitterionic phosphocholine and phosphoethanolamine head groups but differ distinctly from those of phosphoserine which also carries a net negative charge.
Abstract: The structural properties of the phosphoglycerol polar head group in bilayers of 1,2-dipalmitoyl-sn-glycero-3-phosphoglycerol have been studied with deuterium and phosphorus-31 nuclear magnetic resonance. For this purpose, 1,2-dipalmitoyl-sn-glycero-3-phosphoglycerol was deuterated chemically or biosynthetically at all three segments of the glycerol head group. Both the D and the L configurations of the glycerol head group have been synthesized, and the correct stereochemical configuration of the polar group was verified by an enzymtic assay, as direct measurement of the optical rotation was insufficiently sensitive to distinguish between these diastereomers. The phosphatidylglycerol sodium salts were dispersed in excess buffer (0.1 M NaCl, pH 7.0), and the bilayer properties were characterized by small-angle X-ray diffraction and differential scanning calorimetry. The deuterium quadrupole splittings, delta vQ, and the phosphorus-31 chemical shielding anisotropy, delta sigma, were measured as a function of temperature in the range 20-60 degrees C, yielding the following results. (1) Well-resolved deuterium signals were obtained for all head-group segments and could be assigned unambiguously. (2) Almost identical spectra were obtained for 1,2-dipalmitoyl-sn-glycero-3-phospho-1'-glycerol (natural L,D configuration) and 1,2-dipalmitoyl-sn-glycero-3-phospho-3'-glycerol (L,L configuration), suggesting very similar head-group motions and orientations for both diastereomers. (3) The spatial anisotropy of motion and the segmental fluctuations of the negatively charged phosphoglycerol are similar to those of the zwitterionic phosphocholine and phosphoethanolamine head groups but differ distinctly from those of phosphoserine which also carries a net negative charge. (4) The motional inequivalence of geminal deuterons in 1,2-dipalmitoyl-sn-glycero-3-phospho-3'-glycerol was demonstrated by synthesis of a stereospecifically monolabeled analogue.
77 citations
TL;DR: In this article, the quadrupole moment of the 5/2+ 245 keV level of 111Cd in Zn and Be was derived, including sign asQ = +0.83(13) b and the sign of electric field gradient for Cd in Be.
Abstract: The 48.7 m111m
Cd activity was implanted in Zn and Be single crystals which were soldered to the cold finger of a dilution refrigerator and kept below 0.2 K during implantation. Subsequent nuclear orientation experiments allowed the determination of the quadrupole interaction frequencyv
Q
of the 11/2− isomeric state of111Cd in Zn and Be as −139 (15) MHz and +43(16) MHz respectively. With these results we derive the quadrupole moment of the 5/2+ 245 keV level of111Cd including sign asQ = +0.83(13) b and the sign of the electric field gradient for Cd in Be. The half-life of111m
Cd was redetermined as 48.67 (6) m.
75 citations
TL;DR: The microwave spectra of the 13C-species of CF3Br and CF3I have been measured with the aid of radiofrequency pumping of the quadrupole sub-levels as mentioned in this paper.
Abstract: The microwave spectra of the 13C-species of CF3Br and CF3I have been measured with the aid of radiofrequency pumping of the quadrupole sub-levels. In addition, rotational data for the main species have been refined. The following zero-point average structures (rz) have been determined: CF3Br: C—F = 1.3265(23), C—Br = 1.9234(31)A, ∠FCF = 108.81(25)°, CF3I: C—F = 1.3285(23), C—I = 2.1438(27)A, ∠FCF = 108.42(23)°.Particular attention has been paid to the effect of isotopic variation in bond length in the structural calculations. The structures agree well with those recently obtained by combining electron diffraction and microwave data.Accurate Stark measurements have been performed for a number of transitions including the J= 3 → 4, K= 3, F= 7/2 → 9/2 transition of CF379Br and the J= 4 → 5, K= 3, F= 3/2 → 5/2 transition of CF3I. The results have been fitted using a diagonalization treatment of the quadrupole-Stark matrix, set up in the uncoupled basis. The dipole moment of CF3Br was determined to be 0.639(2) D and that of CF3I, 1.048(3) D. The structural properties of CF3Br and CF3I are shown to fit some trends with related molecules.
TL;DR: In this article, the rotational spectra of XeH35Cl, 129XeH37Cl, 128XeD35Cl and 132XeCl van der Waals molecules were derived from a Fabry-Perot cavity with a pulsed supersonic nozzle.
Abstract: Rotational spectra have been assigned for the 129XeH35Cl, 129XeH37Cl, 129XeD35Cl, 131XeH35Cl and 132XeH35Cl van der Waals molecules by employing pulsed microwave Fourier transform spectroscopy in a Fabry–Perot cavity with a pulsed supersonic nozzle as the molecular source. The rotational constants, centrifugal distortion constants, and Cl nuclear quadrupole coupling constants obtained from the spectra are used to determine the structure of XeHCl and to gain information on the intermolecular potential binding of Xe to HCl. From the spectrum of 131XeH35Cl and an analysis of the centrifugal distortion in 129XeH35Cl, 131XeH35Cl, and 132XeH35Cl the 131Xe nuclear quadrupole coupling constant in XeHCl is found to be −4.9±0.2 MHz. Using the known nuclear quadrupole moment of 131Xe, the electric field gradient at the Xe nucleus is calculated. The observed field gradient is discussed in terms of Sternheimer shielding and formation of the weak Xe–HCl van der Waals bond.
TL;DR: In this article, the quadrupole moments increase with increasing spin and imply a substantial (oblate) deformation (..beta.. approx. -0.2) for the 500-ns high-spin yrast trap.
Abstract: Static quadrupole interactions of three /sup 147/Gd isomers in single crystals of hexagonal gadolinium have been observed. The quadrupole moments increase with increasing spin and imply a substantial (oblate) deformation (..beta.. approx. -0.2) for the 500-ns high-spin yrast trap.
TL;DR: In this paper, the Xα multiple scattering wave functions and molecular properties are reported for benzene, pyridine, pyrazine and pyrrole for planar conjugated organic molecules.
Abstract: Xα multiple scattering wave functions and molecular properties are reported for benzene, pyridine, pyrazine, pyrrole, and imidazole. The calculations demonstrate that useful results can be obtained for planar conjugated organic molecules with the Xα method. Values are obtained for ionization potentials and one electron properties, including dipole and quadrupole moments, diamagnetic susceptibilities and nuclear quadrupole coupling constants. In general the results are in better agreement with experiment than minimum basis set Hartree–Fock calculations; this generalization is not true for molecular properties that are dominated by hydrogen atoms, such as deuteron quadrupole coupling constants. The sensitivity of the results to changes in sphere overlap is studied in detail for pyridine and it is found that useful accuracy can be achieved over a fairly broad range of overlap parameters. Calculated ionization potentials agree well with recent assignments of the photoelectron spectra, except for the relative ...
TL;DR: In this article, the authors derived the equations governing the second order perturbation of a slowly rotating, pressureless, constant density star and applied them to the case of the collapse of a uniformly rotating constant-density star following the sudden turnoff of pressure.
Abstract: We study the gravitational waves generated during the collapse of a slowly rotating, pressureless, constant density star. To first order in the rotation rate the perturbation is an odd-parity dipole and generates no gravitational waves. The first order perturbation, however, drives a quadrupole deformation which is second order in the rotation rate and which produces the radiation. Using a gauge invariant description, we derive the equations governing this second order perturbation. These equations are then applied to the case of the collapse of a slowly and uniformly rotating constant-density star following the sudden turnoff of pressure. Numerical results are given for the gravitational waveforms and energies generated.
TL;DR: In this paper, the strengths and limitations of the classical photographic field measurement technique are compared to those of various photoelectric methods developed during the past decade, particularly the Balmer-line Zeeman analyzer technique.
Abstract: A review is presented of techniques of measuring magnetic fields in nondegenerate stars. The strengths and limitations of the classical photographic field measurement technique are compared to those of various photoelectric methods developed during the past decade, particularly the Balmer-line Zeeman analyzer technique. The problem of modeling magnetic data to infer the magnetic field geometry of an observed star is discussed. In the few cases where sufficient data are available to test the centered dipole geometry, it is found to be inadequate. It appears that most magnetic stars have field geometries at least as complex as the oblique decentered dipole (or dipole plus parallel linear quadrupole) model.
TL;DR: The isotope shift in the Ca-intercombination line withλ = 6,573 A was measured for all isotopes between 40Ca and 48Ca with the only exception of 47Ca.
Abstract: The isotope shift in the Ca-intercombination line withλ=6,573 A was measured for all isotopes between40Ca and48Ca with the only exception of 47Ca. The combination of the results with muonic x-ray data yields highly accurate values for the changes of the mean square nuclear charge radii. In addition, the nuclear quadrupole moments of the three isotopes41Ca,43Ca and45Ca have been determined from the hyperfine structure splitting of the 4s 4p
3
P
1 state.
TL;DR: In this article, phase-space dynamics has been extended to provide equations for the ion density distributions theoretically expected in the cases of one-, two-and three-dimensional radio-frequency quadrupole electric fields.
TL;DR: In this article, the mass spectrum of n-hexane recorded with one of the traps has been studied in detail and the conditions necessary to improve performance have been found to parallel those required for the QUISTOR, having quadrupole geometry.
TL;DR: In this article, rotational spectra assignable to gas phase cis-and trans-ethylidenimine (CH3CH=NH) have been detected in the pyrolysis decomposition products from several alkylamines and from the ring trimer.
Abstract: Microwave rotational spectra assignable to gas phase cis‐ and trans‐ethylidenimine (CH3CH=NH) have been detected in the pyrolysis decomposition products from several alkylamines and from the ring trimer, (CH3CHNH)3. Stark effects, hyperfine and internal rotation splittings have aided the assignment of the observed spectra and allowed the determination of rotational distortion constants, 14N nuclear electric quadrupole coupling constants, internal rotation barriers, and electric dipole moments. Limited structural information was also obtained.
TL;DR: In this article, a time-of-flight technique for the determination of forbidden (ms time range) collision-free radiative lifetimes is presented, where the spectrum of metastable atoms generated from a molecular beam source is compared with that for a nonradiating (ground or metastable) state, and the lifetime is derived from a semi-logarithmic plot of the ratio of intensities against flight time.
Abstract: A time-of-flight technique for the determination of forbidden (ms time range) collision-free radiative lifetimes is presented. In this method, the time-of-flight spectrum of metastable atoms generated from a molecular beam source is compared with that for a non-radiating (ground or metastable) state, and the lifetime is derived from a semi-logarithmic plot of the ratio of intensities against flight time. The lifetimes of the calcium 4s4p 3P1 and 4d3d 1D states are determined to be 0.50+or-0.04 (2 sigma ) and 2.3+or-0.5 (2 sigma ) ms. The former result is in reasonable agreement with earlier determinations of this lifetime. One radiative decay pathway for the 1D state is direct electric quadrupole radiation to the ground state. The transition rate for this process has been determined by a MCSCF/CI calculation.
TL;DR: In this article, the results of an endor measurement of a ligand nitrogen were obtained at 4 K. The results showed a pseudonuclear spin-spin interaction between 63Cu and 14N nuclei.
Abstract: EPR experiments have been performed in l‐alanine single crystals doped with copper in order to measure the gyromagnetic tensor of Cu(ii) and the hyperfine coupling tensor with 63Cu. The hyperfine coupling and the nuclear quadrupole interaction tensors of a ligand nitrogen have been obtained by ENDOR at 4 K. The principal values of the hyperfine coupling of 14N are: AN(1)=27 190 KHz, AN(2)=27 560 KHz, and AN(3)=41 740 KHz and those for the nuclear quadrupole interaction are PN(1)=97 KHz, PN(2)=987 KHz and PN(3)=−1084 KHz. The principal directions of the four tensors evaluated in this work are noncoincident. ENDOR resonances of another nitrogen ligand and at least three protons have been detected. Our ENDOR measurements show a pseudonuclear spin–spin interaction between 63Cu and 14N nuclei. This effect is very large and arises from a high order mechanism involving the hyperfine couplings of the unpaired electrons of Cu(ii) with those nuclei. The data are explained with a second order perturbation calculation and it is shown that these effects should be considered in systems with low symmetry where the electrons are coupled to more than one magnetic nuclei.
TL;DR: In this paper, an infrared-radiofrequency double resonance inside a CO 2 N 2 O laser cavity has been applied to the observation of pure nuclear quadrupole resonance and direct A 1 - A 2 transitions of CH 3 Br.
TL;DR: In this paper, a three-fold axis of symmetry along the 〈111〉 direction is characterized by a strong electric quadrupole interaction and a remarkably high trapping probability: almost 100%.
TL;DR: In this article, the Paschen alpha, beta, and gamma lines were observed over an electron density range of (1--8) x 10/sup 22/m/sup -3.
Abstract: Systematic red shifts for the Paschen ..cap alpha.., ..beta.., and ..gamma.. lines (n=4,5,6..-->..n=3) of He II are observed over an electron density range of (1--8) x 10/sup 22/ m/sup -3/. The measurements are compared with combined estimates for plasma polarization and ion quadrupole effects. It is demonstrated that previous theoretical estimates have left out an important contribution to the polarization shift, which we estimate using the Debye model.
TL;DR: In this paper, the microwave and radiofrequency Stark spectra of four isotopic species of the weakly bound complex argon-hydrogen bromide (Ar · H 79Br, Ar · H 81Br, AR · D 79Br and Ar · D 81Br) have been studied using the technique of molecular beam electric resonance spectroscopy.
Abstract: The microwave and radiofrequency Stark spectra of four isotopic species of the weakly bound complex argon-hydrogen bromide (Ar · H 79Br, Ar · H 81Br, Ar · D 79Br, Ar · D 81Br) have been studied using the technique of molecular beam electric resonance spectroscopy. Only transitions within the ground vibrational state have been observed. The analysis of these spectra has led to the determination of rotational constants, centrifugal distortion constants, quadrupole coupling constants (for both bromine and deuterium nuclei), and dipole moments for each isotopic species. In addition the centrifugal distortion of the halogen quadrupole coupling constant has been determined. These data are consistent with a linear equilibrium geometry for the complex with atomic arrangement ArHBr. The vibrationally averaged structure of the complex, however, is non linear due to large amplitude zero-point motion of the hydrogen (deuterium) atom. The derivation of this vibrationally averaged structure from the spectroscopic const...
TL;DR: In this paper, an argument is presented to determine the accuracy with which a solution of Einstein's field equations of gravitation must be approximated in order to describe the dominant effects of gravitational radiation emission from weak-field systems.
Abstract: An argument is presented to determine the accuracy with which a solution of Einstein's field equations of gravitation must be approximated in order to describe the dominant effects of gravitational radiation emission from weak-field systems. Several previous calculations are compared in the light of this argument, and some apparent discrepancies among them are resolved. The majority of these calculations support the 'quadrupole formulae' for gravitational radiation energy loss and radiation reaction.
TL;DR: In this article, the energy-loss spectra of C2H4 and C2D4 are presented covering the energy loss range 6-11 eV, using incident electron energies in the range 5-100 eV above threshold, and scattering angles up to 60 degrees.
Abstract: Energy-loss spectra of C2H4 and C2D4 are presented covering the energy-loss range 6-11 eV, using incident electron energies in the range 5-100 eV above threshold, and scattering angles up to 60 degrees . Members of several optically assigned Rydberg series were identified, and their intensities measured at a number of scattering angles. Each transition was then classified as electric dipole or quadrupole allowed, and this information was used to assign the Rydberg orbitals involved. Four new triplet Rydberg states have been observed, and their assignments are also discussed. For two of the triplet states, more than one vibrational level was observed, and where possible the frequencies of the symmetric C=C stretch and CH2 torsional modes were obtained. For the lowest triplet Rydberg state, the barrier to internal rotation of the CH2 groups was estimated to be 0.08 eV.
TL;DR: In this paper, a cylindrical NMR sample spinner employing gas bearings is described and its application to high-resolution deuterium NMR in solids by magic angle spinning is demonstrated.