Showing papers on "Nuclear quadrupole resonance published in 1974"
TL;DR: In this article, synthesis methods for cesium tin(II) trihalides via aqueous solution and from the melts of anhydrous halides, which ensure freedom from oxidation and the effects of traces of water, are described.
165 citations
TL;DR: In this paper, the effects of univalent cations on divalent anions in the space group Fm3m have been analyzed by nuclear quadrupole resonance and vibrational spectroscopy.
56 citations
TL;DR: In this article, the effect of spin lattice relaxation rates on pure quadrupole resonance pulse experiments for spins with I = 1 is given, in which the three dimensional relaxation problem is reduced to a two dimensional one.
Abstract: A quantitative analysis of the effect of spin lattice relaxation rates on pure quadrupole resonance pulse experiments for spins with I = 1 is given. A model is presented in which the three dimensional relaxation problem is reduced to a two dimensional one. In this model any possible population distribution of the energy levels corresponds to a point in a plane, the ``ν plane.'' The response of the system to spin‐lattice relaxation effects and to rf pulses are described as translations of points in this plane. The experimental signal intensities are directly related to the coordinates of those points. The following cases are treated quantitatively: (i) CW saturation, (ii) CW saturation followed by a 90° pulse, (iii) two‐pulse sequences, and (iv) continuous steady state pulse sequences. For each case explicit equations for the signal intensity as function of the experimental parameters are given. The analysis is made for both single crystals and powders.
48 citations
26 citations
25 citations
TL;DR: Theoretical absorption line shapes are presented for Zeeman perturbed nuclear quadrupole resonance transitions (I = 3/2) in polycrystalline materials for the case in which the rf field is parallel to the Zeeman field as mentioned in this paper.
Abstract: Theoretical absorption line shapes are presented for Zeeman perturbed nuclear quadrupole resonance transitions (I = 3/2) in polycrystalline materials for the case in which the rf field is parallel to the Zeeman field. For a nuclear spin of 3/2, the pure quadrupole transition frequency νQ(1+η2/3)1/2 is insufficient to independently determine either νQ, the strength of the quadrupole interaction, or η, the asymmetry in the electric field gradient tensor. Application of a magnetic field removes the degeneracy of the energy levels producing, in general, four orientation dependent transition frequencies from which the quadrupole parameters can be determined. Computer simulated powder lineshapes are presented which are exact in η and are to first order in applied magnetic field strength. Frequencies of the features of the line shape are plotted as a function of η. The features of the line shape are due to crystallites aligned such that the applied field is parallel to one of the principal axes of the electric f...
24 citations
23 citations
TL;DR: The temperature dependence of the 187 Re ( + 5 2 ↔ ± 3 2 ) nuclear quadrupole resonance transition frequency has been measured from 387°K down to 245°K.
19 citations
TL;DR: In this article, a precise redetermination of the 119mSn Mossbauer spectral parameters of a large number of organotin (IV) halides and of the tin tetrahalides has been made.
Abstract: A precise redetermination of the 119mSn Mossbauer spectral parameters of a large number of organotin (IV) halides and of the tin (IV) tetrahalides has been made. The 35Cl NQR resonance spectra of (CH3)3SnCl and of (n‐C5H11)2SnCL2 have been measured for the first time. These data, in conjunction with literature values of other halogen frequencies in this series, yield correlations of both the central tin atom Mossbauer isomer shift and quadrupole splitting values with the reduced ligand NQR coupling constants. The correlations may be interpreted qualitatively in terms of the bonding trends expected on the basis of ligand electronegativities, and the uniformities of the correlations strongly indicate a lack of sharply defined structural variations within these compounds.
17 citations
TL;DR: In this paper, the temperature dependence of nqr frequencies in nuclear quadrupole resonance has been studied in ferroelectric sodium nitrite (NaNO 2 ) from 77 K to its phase transition point 437 K.
Abstract: Nuclear quadrupole resonance has been studied in ferroelectric sodium nitrite (NaNO 2 ) from 77 K to its phase transition point 437 K. The three rotational frequencies ω a =190 cm -1 , ω b =120 cm -1 and ω c =227 cm -1 and their temperature variation when fitted in the Bayer-Kushida theory predict the temperature dependence of nqr frequencies reasonably well. A second order phase transition is found to occur at 180 K which is in confirmity with the one found earlier from thermal expansion and dielectric studies. The shift in resonance frequencies is seen to occur mainly by rotation around the ` c ' axis and hence it is inferred that the mechanism of polarization reversal is intimately connected with orientational motion about ` c ' axis.
TL;DR: In this article, a new technique for the determination of the asymmetry parameter (η) of the electric-field gradient tensor is presented, based on a single good experimental spectrum at moderately high magnetic field.
TL;DR: In this article, the 35 Cl nuclear quadrupole resonance frequencies and relaxation times in ammonium hydrogen bis (chloroacetate) were measured in the ferro- and the paraelectric phases.
Abstract: The 35 Cl nuclear quadrupole resonance frequencies and relaxation times in ammonium hydrogen bis (chloroacetate) were measured in the ferro- and the paraelectric phases. The splitting of the resonance line in the ferroelectric phase shows the temperature dependence in the form of Δ ν=( T c - T ) 1/3 near the transition point T c . Sharp decrease of T 1 has been observed in the critical region and it was attributed to the critical slowing down of the electric dipolar interactions. Two kinds of relaxation mechanisms were examined: The order-disorder type of mechanism can explain the T 1 data of the paraelectric phase but it fails to explain the different temperature dependence of T 1 of ν 1 and ν 2 in the ferroelectric phase. The other mechanism, the displacive-mode transition is plausible because it gives a reasonable description of the T 1 anomaly both in the ferro- and paraelectric phases. This mechanism is also consistent with the structural evidences.
TL;DR: In this paper, the Zeeman effect on the nuclear quadrupole resonance of both 35Cl and 14N nuclei in a single crystal of pchloroaniline has been studied at room temperature.
Abstract: The Zeeman effect on the nuclear quadrupole resonance of both 35Cl and 14N nuclei in a single crystal of p‐chloroaniline has been studied at room temperature. A spectrometer was employed which was capable of working at the resonance frequency of either nucleus without altering the position of the crystal. Novel features of the spectrometer were both a frequency stabilizing apparatus working at the 14N resonance frequency and the attachment of an electronic computer for direct and accurate ``on‐line'' determination of spectral parameters. The relative orientations of the electric field gradient tensors on both nuclei have been obtained. Furthermore, by studying the 14N linewidth dependence on the static magnetic field orientation, information has also been gained about the position of the −NH2 protons in the electric field gradient tensor principal axes mainframe. Some remarkable experimental results can be interpreted theoretically when the treatment of the magnetic dipole interaction between 14N and 1H i...
TL;DR: In this article, the authors measured the T1 in hexamethylenetetramine (HMT) as a function of hydrostatic pressure up to 6 katm at 257, 273, 294, and 317°K.
Abstract: 14N nuclear quadrupole resonance frequencies and spin‐lattice relaxation time, T1, in hexamethylenetetramine (HMT) were measured as a function of hydrostatic pressure up to 6 katm at 257, 273, 294.5, 309, and 317°K. For the three higher isotherms T1 depends exponentially on pressure up to 3 katm. In this region T1 is determined mainly by molecular reorientation of the tetrahedral HMT molecule around its four threefold axes. This mechanism is discussed in terms of a simple activation process. The activation volume, ΔV*=23.6±1 cm3/mole, and activation enthalpy, ΔH*=17±1 kcal/mole were determined. From thermal expansion and compressibility data, the thermal pressure, Pt = T(∂p/∂T)v, of 6.2 katm and activation energy ΔE* = 12–15 kcal/mole were deduced. These values of ΔH*, ΔE*, and ΔV* are higher than the corresponding values reported by Anderson and Slichter for three other organic solids and might indicate the effect of the large number of hydrogen bonds in HMT.
TL;DR: The frequency of 14N nuclear quadrupole resonances ν+ and ν− in pyrazine has been measured at several temperatures between 4.2 and 324 K as discussed by the authors.
Abstract: The frequency of the 14N nuclear quadrupole resonances ν+ and ν− in pyrazine has been measured at several temperatures between 4.2 and 324 K. Below 300 K, only one ν+ line and one ν− line are seen, indicating the existence of a unique sort of crystalline site for nitrogen atoms in the crystal of pyrazine. At 27° and 35°C crystalline phase transitions are observed through a splitting of the lines and a discontinuity of the frequency of resonance. An interpretation of the temperature dependence of the resonance frequencies, ν+ and ν−, between 4.2 and 300 K is proposed using Bayer's theory and the molecular motion frequencies reported by Ito and Shigeoka; however, the assignment of these frequencies to specific rotations about the different axes of symmetry of the molecule, which fits nuclear quadrupole resonance data, is different from that given by Ito and Shigeoka.
TL;DR: In this paper, the paramagnetic centers trapped in X- or γ-irradiated calcium chlorate dihydrate, Ca(ClO 3 )( 2 ·2H 2 O, single crystals have been studied using electron spin resonance methods.
TL;DR: In this article, the contribution of the acoustic branch frequencies to the librational motional averaging of the nuclear quadrupole resonance Hamiltonian in molecular crystals is examined in two simple linear chain models.
TL;DR: In this paper, the nuclear quadrupole resonances of ZnBr2 and PbBr2 at 77, 195 and 298 K were observed in both ZnBR2 and pbBR2 with relative intensities 1 : 2 : 1.
Abstract: Nuclear quadrupole resonances of 79Br and 81Br have been observed in both ZnBr2 and PbBr2 at 77, 195 and 298 K. For ZnBr2 three closely spaced lines at 81.425, 83.100 and 84.137 MHz (81Br, 77 K) of relative intensities 1 : 2 : 1 are in accord with three non-equivalent lattice sites of space group I41/acd. For PbBr2 two lines observed at 20.669 and 27.824 MHz (81Br, 77 K), consistent with space group P bnm, have been assigned to their respective lattice sites on the basis of point-charge model calculations.
TL;DR: In this paper, a pulsed free decay nuclear magnetic resonance system has been used to study the 14N nuclear quadrupole resonance in N, N1−dimethylpiperazine.
Abstract: A pulsed free decay nuclear magnetic resonance system has been used to study the 14N nuclear quadrupole resonance in N, N1‐dimethylpiperazine. The quadrupole frequencies and spin‐lattice relaxation times are measured from 77°K up to the melting point (∼276°K). The relaxation times are determined by the rotation of the CH3 group (120–200°K) and the hindered rotation of the whole molecule (above 200°K). The spin relaxation of the liquid state is also reported.
TL;DR: In this paper, the vibrational spectrum of CH3InI2 has been used to detect linear In(CH3)+2 ions rather than being a bridged halogen dimer as is found for most other compounds of this type.
TL;DR: In this article, the Sb Mossbauer spectra have been measured at 4·2 K in some cyanide adducts SbCl5,NCR (R = Me, Cl, But, Ph, Et, CH2Cl, CCl3, CHCH2).
Abstract: 121 Sb Mossbauer spectra have been measured at 4·2 K in some cyanide adducts SbCl5,NCR (R = Me, Cl, But, Ph, Et, CH2Cl, CCl3, CHCH2). Hyperfine interactions deduced from transmission integral analysis of the spectra are interpreted in terms of the varying degree of electron transfer from the cyanide to the antimony atom. The results are discussed in combination with data from nuclear quadrupole resonance and vibrational spectroscopy studies.
TL;DR: The microwave rotational spectra of the two most abundant isotopic species of propiolyl chloride have yielded rotational constants and nuclear quadrupole coupling constants as discussed by the authors, in combination with the chloride NQ resonance spectra, have yielded the molecular structure.
TL;DR: In this article, the Zeeman effect on the N.R.Q. of methyl 4-bromobenzoate, 4,4′-dibromodiphenylether, and 4, 4′-Dibrommodiphenylsulphide has been studied at 77 K on single crystals, using the "geometric method".
Abstract: The Zeeman effect on the N.Q.R. of methyl 4-bromobenzoate, 4,4′-dibromodiphenylether, 4,4′-dibromodiphenylsulphide has been studied at 77 K on single crystals, using the ‘geometric method’. The apparatus used in the measurements, which allows one to maintain any temperature between room temperature and 77 K, is described, and the possible significance of the slight variations in the molecular arrangement found in the present measurements and in those performed at room temperature is discussed.
TL;DR: In this article, a simple point-charge model is used to derive a semiquantitative measure of the interaction between XeF+ and NbF6− or Nb2F11− ions in xenon difluoride-niobium pentafluorside complexes.
Abstract: 93 Nb N.q.r. spectra of NbF5, XeF2, NbF5, XeF2, 2NbF5, NbF5, L (L = Me2O or CH2ClCN), and NbF5,2py have been obtained. The results are consistent with low values of the asymmetry parameter (η) for the electric field gradient tensor at the 93Nb nuclei in all compounds investigated. A simple point-charge model is used to derive a semiquantitative measure of the interaction between XeF+ and NbF6– or Nb2F11– ions in xenon difluoride–niobium pentafluoride complexes.
TL;DR: In this article, it is reported that the 35Cl NOR line height decreased with added impurity molecules, and the decrease in the line height is explained by the disturbance of the field gradient due to the volume difference between the resonant and impurity molecule.
Abstract: It is reported that the 35Cl NOR line height decreased with added impurity molecules, and the decrease in the line height is explained by the disturbance of the field gradient due to the volume difference between the resonant and impurity molecules. In the present experiment, it is found that there are three types of effects on the NOR line intensity due to impurities; (I) The substitution effect is caused by replacing the resonant atom in the host molecule with a non-resonant atom in an impurity molecule, which may be very intense. (II) An indirect disturbance is caused by the formation of a solid solution which may be mild. (III) The mixture effect may be very small, and hardly disturbs the field gradients.