共查询到20条相似文献,搜索用时 31 毫秒
1.
The temperature dependences of the14N nuclear quadrupole resonance frequencies have been measured in phases II, III, IV and V of ammonium nitrate with the help of the1H–14H nuclear quadrupole double resonance technique. The experimental results are related to the proposed crystal structures and disorder in the various crystallographic phases. 相似文献
2.
Using Cu nuclear quadrupole resonance (NQR) in Eu-doped La2-xSrxCuO4 we find the evidence of the pinned stripe phase at 1.3 K for 0. 08=x=0.18. The pinned fraction increases by 1 order of magnitude near hole doping x = 1/8. The NQR line shape reveals three inequivalent Cu positions: (i) sites in the charged stripe, (ii) nonmagnetic sites outside the stripes, and (iii) sites with a magnetic moment of 0.29&mgr;(B) in the antiferromagnetically correlated regions. A dramatic change of the NQR signal for x>0.18 correlating with the onset of bulk superconductivity corresponds to the depinning of the stripe phase. 相似文献
3.
J. Seliger V. Žagar R. Blinc R. Kind H. Arend F. Milia 《Zeitschrift für Physik B Condensed Matter》1987,67(3):363-368
The structural phase transitions between the non-intercalated phases of the layer structure compound N-octylammoniumchloride have been studied via proton-14N and proton-35Cl nuclear quadrupole double resonance. The results have been related to an order-disorder model of the octylammonium chains. The temperature dependence of the order parameters of the –NH3 head groups has been determined. 相似文献
4.
J. Seliger V. Žagar R. Blinc R. Kind H. Arend G. Chapuis K. J. Schenk F. Milia 《Zeitschrift für Physik B Condensed Matter》1987,69(2-3):379-384
The structural phase transitions between the intercalated and the non-intercalated phases of the layer structure compound n-decylammoniumchloride and n-hexylammoniumchloride have been studied via proton-14N and proton-35Cl nuclear quadrupole double resonance. The results have been related to an order-disorder model of the alkylammonium chains. The temperature dependence of the order parameters of the –NH3 head groups has been determined. 相似文献
5.
Recent work of the Ljubljana group in the nuclear quadrupole double resonance detection of explosives, mines, narcotics and drugs is reviewed with particular emphasis on enhancing low-frequency nuclear quadrupole resonance signals. 相似文献
6.
J. Etrillard C. Meinel C. Odin H. Zimmermann B. Toudic J. C. Ameline 《Applied magnetic resonance》1999,17(2-3):301-313
Nuclear magnetic resonance (NMR) experiments,35C1 nuclear quadrupole resonance (NQR) and2H NMR, have been performed close to the displacive normal-incommensurate phase transition in the organic crystal of bis-(4-chlorophenyl)-sulfone. Calculations using coherent neutron scattering results show that the soft-mode contribution cannot explain the rapid increase of the spin-lattice relaxation rates close to the transition temperature. Calculations of the spectral densities taking into account the existence of a central-peak phenomenon describe both35C1 NQR and2H NMR spin-lattice relaxation rates on approaching the phase transition. In this way, the width of the central peak can be estimated to be in the range of several gigahertz. 相似文献
7.
Salman Z Kiefl RF Chow KH Hossain MD Keeler TA Kreitzman SR Levy CD Miller RI Parolin TJ Pearson MR Saadaoui H Schultz JD Smadella M Wang D MacFarlane WA 《Physical review letters》2006,96(14):147601
We demonstrate that zero-field beta-detected nuclear quadrupole resonance and spin relaxation of low energy (8)Li can be used as a sensitive local probe of structural phase transitions near a surface. We find that the transition near the surface of a SrTiO(3) single crystal occurs at T(c) approximately 150K, i.e., approximately 45K higher than T(c)bulk, and that the tetragonal domains formed below T(c) are randomly oriented. 相似文献
8.
Deuteron magnetic resonance spectrum of monodeuteroethene in isotropic phase solution is shown to give the relative signs of the indirect spin-spin coupling constants, while the proton spectrum cannot provide this information. In agreement with previous experimental and theoretical evidence, J gem is found to have the same sign as the two vicinal coupling constants. High resolution deuteron resonance spectra of monodeuteroethene in the nematic phase solution are analysed in terms of the order matrix and quadrupole splitting. The quadrupole coupling constant and the asymmetry parameter are determined by two partly independent methods. 相似文献
9.
M. A. Chuev 《JETP Letters》2005,82(10):658-663
It is shown that the harmonic librations (oscillations) of the principal axis of the electric field gradient tensor in “cages” of liquids, glasses, ferroliquids, and other “soft” systems qualitatively change the shape of the Mössbauer spectra of the quadrupole hyperfine structure. In addition to an effective decrease in the quadrupole coupling constant in the fast-libration limit, nuclear quadrupole resonance is predicted, which must be manifested in the Mössbauer spectra at the libration frequency that is approximately equal to the quadrupole splitting of spectral lines. By analogy with nuclear magnetic resonance, simple analytical expressions are derived, which describe resonance Mössbauer spectra in terms of the effective quadrupole coupling constant and the resonance splitting constant for the main lines. The observed features of the formation of quadrupole hyperfine structure spectra can be manifested in the Mössbauer spectra of soft matter and must be taken into account in analysis of experimental data. 相似文献
10.
A relationship between the phase factor of a quantum gate, the layout of energy levels of its effective Hamiltonian, and the implementation time of the gate is demonstrated. By an example of the direct and inverse quantum Fourier transforms (QFT) gates for a qutrit represented by a quadrupole nucleus with spin I = 1, as well as for a system of two qubits (I = 1/2), effective Hamiltonians and minimum implementation times corresponding to different global phases are obtained. Implementation schemes are proposed for these Hamiltonians by the nuclear magnetic resonance (NMR) technique with the use of sequences of radio-frequency (RF) pulses separated by intervals of free evolution. Analytic results for the minimum times of gates are in agreement with the results obtained by numerical optimization methods. The phase considered is divided into dynamic and geometric parts. 相似文献
11.
The sensitivity of the Slusher and Hahn’s nuclear quadrupole double resonance technique is calculated in general for an arbitrary nuclear spin S of the quadrupole nuclei and for an arbitrary asymmetry parameter η of the electric field gradient tensor. The nuclear spin S = 5/2 (17O, 25Mg, …) is treated in details. The influence of the cross-relaxation rate between the quadrupole nuclei and the abundant spin system on the sensitivity of double resonance is discussed. The results of the theoretical analysis are applied in the analysis of the 1H–17O nuclear quadrupole double resonance spectra in p-toluenesulfonamide and 2-nitrobenzoic acid. The 17O nuclear quadrupole resonance frequencies from a sulfonamide group are determined for the first time. The proton–oxygen cross-relaxation rates and the proton local frequency in zero external magnetic field are experimentally determined from the nuclear quadrupole double resonance spectra. 相似文献
12.
13.
The temperature dependence of the17O nuclear quadrupole resonance (NQR) frequencies has been measured in commercial trinitrotoluene by highly sensitive nuclear
quadrupole double resonance techniques. The14N NQR frequencies have been measured in the same sample for comparison. In contrast to the14N quadrupole coupling constant, the17O quadrupole constant increases with increasing temperature. 相似文献
14.
Jun Hee Han J.S. Kim Jun Kue Park Kyu Won Lee J.-I. Jin E.H. Choi Cheol Eui Lee 《Current Applied Physics》2014,14(10):1356-1359
Nuclear magnetic resonance (NMR) spectroscopy has provided a unique opportunity to study the characteristic smectic-A to chiral nematic phase transition in a dimesogenic liquid crystal (“KI-5S”). The order parameters in the liquid crystalline phases were obtained from the 2H NMR quadrupole splitting and 13C NMR chemical shift measurements, manifesting a first-order smectic-nematic phase transition. 相似文献
15.
The phase diagrams of vanadium-hydrogen (V-H) and vanadium-deuterium (V-D) have been investigated by measuring the nuclear magnetic resonance (NMR) spectra of vanadium and deuterium in strongly textured vanadium foils. In the cubic α- and α′-phases both the V and D lines are unsplit. From the orientation dependence of the quadrupole splitting of the two resonances in the tetragonal β-phase it is found that for both atoms the electric field gradient is axially symmetric with its largest component parallel to the c-axis. In contrast to V-H, the β-phase of V-D exists only in a small region near D/V ratios of about 0·4 at 300°K; for higher D concentrations the α′-phase remains stable down to about 200°K, below which the orthorhombic δ-phase is formed. In spite of the nearly cubic arrangement of the V atoms in the δ-phase, the intensity of the vanadium line is reduced corresponding to first-order quadrupole splitting. From the absence of any V satellites in the δ-phase, it follows that the orientation of the principal axes of the field gradient at the V sites deviate strongly from the cube edges of the V lattice. For deuterium the largest component is parallel to one cube edge, which must be the c-axis of the orthorhombic cell. Thus the field gradient at the D sites has the same symmetry in the β- and δ-phase, with quadrupole frequencies of 100 and 55 kHz, respectively. This difference can be attributed to the fact that in the two phases different sites are occupied: octahedral sites in the β-phase and tetrahedral sites in the δ-phase. 相似文献
16.
The angular dependence of the nuclear quadrupole resonance (NQR) signal intensity emitted from polycrystalline hexamethylenetetramine has been analytically investigated for all directions for non-contact detection of chemicals by nuclear quadrupole resonance. The field pattern of the NQR signal from a column sample was measured. The emitted patterns were the same as that from a united single magnetic dipole, which fitted well to the estimation based on quadrupole principle axis system. This result is helpful to design an antenna for NQR remote detection. 相似文献
17.
Temperature dependence of chlorine nuclear quadrupole resonance in 2-chloro 5-nitrobenzoic acid and 4-chloro 3-nitrobenzoic
acid has been investigated in the region 77° K to room temperature. No phase transition has been observed. The results are
analysed to obtain the torsional frequencies and their temperature dependence. A nonlinear temperature dependence is obtained
for the torsional frequencies. 相似文献
18.
Perlo J Casanova F Robert H Pusiol DJ 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2001,150(2):132-136
A double resonance method for imaging of solid materials containing quadrupole nuclei via the coupled protons is reported. The technique uses a static field gradient to encode the position on the protons and the method of double resonance spin-echo to detect the occurrence of proton resonances by affecting the zero-field echo signal from the quadrupole system. The double resonance imaging method offers the advantages of higher spatial resolution and straightforward image reconstruction for powder samples compared with rotating-frame and Zeeman-perturbated nuclear quadrupole resonance encoding techniques. 相似文献
19.
135Ba and137Ba Fourier transform nuclear magnetic resonance and nuclear quadrupole resonance investigations are reported in liquids resp. solids. From these measurements ratios of g1-factors, hyperfine structure anomalies, magnetic moments, atomic shielding constants and the ratio of the quadrupole moments are evaluated using also data from literature. 相似文献
20.
Korneva I Ostafin M Sinyavsky N Nogaj B Maćkowiak M 《Solid state nuclear magnetic resonance》2007,31(3):119-123
The method of two-dimensional nutation nuclear quadrupole resonance in time domain is used to study the chalcogenide semiconductor As(2)Se(3). In this system, the nuclear quadrupole resonance (NQR) resonance line width is as large as 10 MHz; therefore, the radiofrequency field produced by a pulsed NQR spectrometer can excite only a portion of the nuclear spins. The proposed method relies on polarizing the melted glass specimen in a strong magnetic field so that orientational disorder is partially removed. After hardening the sample is placed in a spectrometer r.f. coil in such a way that that the axes of sample polarization and r.f. coil coincide. We demonstrate the application of this method to determine eta in glassy As(2)Se(3). 相似文献