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.
Papers published on a yearly basis
Papers
More filters
TL;DR: In this article, As4Se3 was synthesized and isolated in two polymorphs of which α-As-Se3 is isostructural with α-Se2Se3 and β-As4Se2 is monoclinic, space group C2/c or Cc.
Abstract: Tetra-arsenic triselenide, As4Se3, has been synthesized and isolated in two polymorphs of which α-As4Se3 is isostructural with α-As4Se3. It is orthorhombic, space group Pnma, with Z= 4, in a unit cell of dimensions a= 9.46(2), b= 7.97(2), c= 10.47 (2)A. The 75As n.q.r. spectrum at 77 K shows three resonances with intensities 1 : 2 : 1 at 60.78 and 61.07 MHz due to the basal As and at 68.97 due to the apical As of the As4Se3 molecule. The polymorph β-As4Se3 is monoclinic, space group C2/c or Cc, with Z= 16 in a unit cell of dimensions a= 25.62(5), b= 6.52(2), c= 23.01(5)A, β= 126.6 ± 0.5°. Its n.q.r. spectrum at 77 K shows a number of incompletely resolved lines between 57.5 and 61.0 MHz and between 69.5 and 71.5 MHz, associated with basal and apical As atoms of the As4Se3 molecule.
15 citations
TL;DR: In this paper, a single crystal sample of scandium metal at temperatures down to 100 K using nuclear quadrupole resonance (NQR) was used as an absolute thermometer in the {mu}Kelvin regime.
Abstract: Results are presented of measurements on a single crystal sample of scandium metal at temperatures down to 100 {mu}K using nuclear quadrupole resonance (NQR). Two regimes are found in the relaxation curves; an initial fast relaxation, followed by a slower relaxation consistent with the three exponential recovery expected for an I = 7/2 system in zero external magnetic field. The Korringa constant for this longer time relaxation in the sample is 90 {plus minus} 9 msec K{sup {minus}1}. By observing deviations in the ratio of the intensities of adjacent nuclear spin transitions at the lowest attainable temperatures, the authors were able to make a determination of the sign of the total electric field gradient present in the crystal. Results show that the lowest energy state of the nuclear spin system corresponds to m{sub I} = {plus minus} 7/2. A combination of these deviations and pulse NQR allows this system to be used as an absolute thermometer in the {mu}Kelvin regime.
15 citations
TL;DR: In this article, the nuclear quadrupole resonance (NQR) has been investigated for Cu in La2−x¯¯¯¯A�Ω(Sr and Ba), where three Cu NQR lines, A, B and C, correspond to three different Cu sites.
Abstract: The nuclear quadrupole resonance (NQR) has been investigated for Cu in La2−x
A
x
CuO
y
(A=Sr and Ba). Three Cu NQR lines, A, B and C, have been observed, which correspond to three different Cu sites. From the analysis of these NQR intensities, site assignments are possibly as follows. These lines A, B and C are attributed to CuO6 octahedral, CuO5 pyramidal and CuO4 planar sites, respectively. The apical oxygen O(2) is induced to transfer to the interstitial O(3) site between LaO planes when two or more Sr2+ ions are located in its neighboring La sites. The excess holes doped into the CuO2 plane are provided mainly by O(3) as well as the unpaired Sr2+ ion.
15 citations
TL;DR: In this article, high-pressure studies of X-ray diffraction and 11 B-nuclear magnetic resonance (NMR) in the intermediate-valence compound SmB6 were conducted and no anomaly was observed up to 9.1 GPa.
Abstract: We report high-pressure studies of X-ray diffraction and 11 B-nuclear magnetic resonance (NMR) in the intermediate- valence compound SmB6. The pressure dependence of the lattice constant was precisely determined and no anomaly was observed up to 9.1 GPa. The temperature dependence of the nuclear quadrupole resonance frequencyQ, obtained from the 11 B-NMR measurements, is predominantly contributed by on-site charge distribution. Using the relationship betweenQ and Sm valence at ambient pressure reported previously, we estimate the pressure dependence of the Sm valence up to 6 GPa as well. The increase in the Sm valence accelerates with pressure and reaches an increase of about 10% at 6 GPa. The pressure-induced localization of Sm 4f -holes may be responsible for the long-range magnetic order under pressure.
15 citations
TL;DR: In this article, a model that explains the observed correlation between the P-values and the electronic energy shifts of the defect sites is presented, and a reasonable connection is made with two types of localised defect that are expected to occur frequently in the lattice structure.
Abstract: The intrinsic site and over forty defect sites have been studied by optical absorption, fluorescence and optical hole burning in EuAsO4. The hole-burning spectra have allowed determination of the nuclear electrical quadrupole parameters P and asymmetry parameters eta for the 5D0 levels for both Eu isotopes at 11 of these sites. A model is presented that explains the observed correlation between the P-values and the electronic energy shifts of the defect sites. Nuclear Zeeman effect studies of two sites using nuclear hole-burning spectroscopy in fields up to 8.8 T have allowed the determination of the orientation of their 5D0 electronic quadrupole tensors. Reasonable connection is made with two types of localised defect that are expected to occur frequently in the lattice structure. Energy transfer effects have also been examined as a function of temperature.
15 citations