Topic
Nuclear quadrupole resonance
About: Nuclear quadrupole resonance is a research topic. Over the lifetime, 3531 publications have been published within this topic receiving 38801 citations. The topic is also known as: Nuclear quadrupole resonance spectroscopy & NQR.
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TL;DR: In this article, the authors reported 123 Sb nuclear quadrupole resonance (NQR) measurements of the filled skutterudite heavy-fermion superconductor PrOs 4 Sb 12 under high pressures of 1.91 and 2.34 GPa.
Abstract: We report 123 Sb nuclear quadrupole resonance (NQR) measurements of the filled skutterudite heavy-fermion superconductor PrOs 4 Sb 12 under high pressures of 1.91 and 2.34 GPa. The temperature dependence of NQR frequency and the spin-lattice relaxation rate 1/ T 1 indicate that the crystal-electric-field splitting Δ CEF between the ground state Γ 1 singlet and the first excited state Γ 4 (2) triplet decreases with increasing pressure. The 1/ T 1 below T c = 1.55 K at P = 1.91 GPa shows a power-law temperature variation and is proportional to T 5 at temperatures considerably below T c , which indicates the existence of point nodes in the superconducting gap function. The data can be well fitted by the gap model Δ(θ) = Δ 0 sin θ with Δ 0 = 3.08 k B T c . The relation between the superconductivity and the quadrupole fluctuations associated with the Γ 4 (2) state is discussed.
18 citations
TL;DR: In this article, the perturbative effects of a series of radiofrequency (rf) pulses, electric field gradient inhomogeneity, and dipole-dipole coupling on the spin dynamics of spin-1 nuclei dominated by the quadrupole interaction were theoretically examined.
Abstract: We theoretically examine the perturbative effects of a series of radio-frequency (rf) pulses, electric field gradient inhomogeneity, and dipole-dipole coupling on the spin dynamics of spin-1 nuclei dominated by the quadrupole interaction. The dipole-dipole coupling is between neighboring spin-1 nuclei with identical nuclear quadrupole resonance frequencies, but the principal axes frames of the electric field gradient at each nucleus are not aligned. Such a comprehensive treatment is necessary to determine the optimal sequence of rf pulses which maximizes the echoes in the detection of the substance of interest, for example, an explosive or other contraband material. We confirm our theoretical model using the nitrogen in powder samples of $p$-chloroaniline and sodium nitrite.
18 citations
TL;DR: In this article, the origin of charge inhomogeneity in a very wide NQR line was investigated using an experimental method designed to determine the nuclear quadrupole resonance (NQR) asymmetry parameter.
Abstract: The origin of charge inhomogeneity in $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{y}$ is investigated using an experimental method designed to determine the nuclear quadrupole resonance (NQR) asymmetry parameter $\ensuremath{\eta}$ for very wide NQR lines at different positions on the line. The method is based on the measurement of the echo intensity as a function of the angle between the radio frequency field ${\mathbf{H}}_{1}$ and the principal axis of the electric field gradient. Static charge inhomogeneity deduced from $\ensuremath{\eta}g0$ is found in this compound, but only in conjunction with oxygen deficiency. This limits considerably the possible forms of charge inhomogeneity in bulk $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{y}$.
18 citations
TL;DR: In this article, the universal quadrupole resonance crystal analyzer was described, and using this apparatus the crystal structure of SnBr was studied at room temperature (15°∼20°C).
Abstract: Details of the universal quadrupole resonance crystal analyzer were described, and using this apparatus the crystal structure of SnBr was studied at room temperature (15°∼20°C). The SnBr 4 molecule is an almost exact tetrahedron, and each of the four resonance lines is assigned to each bromine atom situated at the apexes of the tetrahedron, and the value of asymmetry parameter of the field gradient at the bromine nucleus is less than 0.025. The crystal has monoclinic symmetry and one of the Sn-Br bond in one molecule is perpendicular to the b -axis and the other two orient at the same angle to the b -axis. All atoms including Sn in a molecule have nonequivalent general positions in the crystal, and the number of molecules in a unit-cell is equal to the maximum number of equivalent coordinates of the space-group. The existence of pair of two molecules is suggested, and the origin of the splitting of the spectrum is discussed. SnBr 4 may be assigned to the symmetry class C 2 h . The crystal symmetry of the ...
18 citations
TL;DR: Satisfactory correlations between the (sigma NH--sigma NS) electron densities at the sulfamyl nitrogen and the in vitro carbonic anhydrase inhibitory activities of the sulfonamides have been found.
Abstract: Nitrogen-14 nuclear quadrupole resonance (NQR) spectra of several benzenesulfonamides in their solid state are reported and analyzed in the framework of the Townes and Dailey theory. Satisfactory correlations between the (sigma NH--sigma NS) electron densities at the sulfamyl nitrogen and the in vitro carbonic anhydrase inhibitory activities of the sulfonamides have been found. The correlations are in accord with the results of other studies that show the carbonic anhydrase inhibitory activities to be largely influenced by the electronic property of the sulfamyl group.
18 citations