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.

Ligand‐field splittings and core‐level linewidths in I 4d photoelectron spectra of iodine molecules

Abstract: High‐resolution I 4d photoelectron spectra (total instrumental resolution ∼0.06 eV) of seven simple iodine molecules, ICl, IBr, I2, HI, CH3I, CH2I2, and CF3I, have been recorded. Ligand‐field splitting (as measured by the asymmetric C20 crystal‐field term) splits the 4d3/2 and 4d5/2 lines into a doublet and triplet, respectively. In contrast to Si 2p spectra, the I 4d spectra generally show little evidence for vibrational splitting or broadening. The C20 values, like the binding energies E4d, generally increase as the ligand electronegativity increases. C20 also correlates well with the nuclear field gradient, eqn, as measured by Mossbauer spectroscopy or nuclear quadrupole resonance. For the first time we have been able to study the chemical dependence of the inherent lifetime width of a core hole. We show that the I 4d linewidths generally decrease as the electronegativity of the ligand increases, and as the valence I 5p electron density decreases. We also show that there are large relaxation effects on...

Weak Magnetic Order in Bilayered-Hydrate NaxCoO2·yH2O Structure Probed by Co Nuclear Quadrupole Resonance –Proposed Phase Diagram in Superconducting NaxCoO2·yH2O–

Abstract: A weak magnetic order was found in a nonsuperconducting bilayered-hydrate Na x CoO 2 · y H 2 O sample by Co nuclear quadrupole resonance (NQR) measurement. The nuclear spin–lattice relaxation rate divided by temperature 1/ T 1 T shows a prominent peak at 5.5 K, below which a Co NQR peak splits due to an internal field at the Co site. From the analyses of the Co NQR spectrum at 1.5 K, the internal field is evaluated to be ∼300 Oe and found to be in the a b -plane. The magnitude of the internal field suggests that the ordered moment is as small as ∼0.015 µ B using the hyperfine coupling constant reported previously. It is shown that the NQR frequency ν Q correlates with magnetic fluctuations from measurements of NQR spectra and 1/ T 1 T in various samples. The higher-ν Q sample has stronger magnetic fluctuations. A possible phase diagram for Na x CoO 2 · y H 2 O is depicted using T c and ν Q , in which the crystal distortion along the c -axis of the tilted CoO 2 octahedron is considered to be a physical par...

Correlations between 35Cl Nuclear Quadrupole Resonance (NQR) Frequencies of Chlorobenzene Derivatives and Characteristic Reaction Parameters of the Substituents

Abstract: The 35Cl NQR frequencies (at 77°K) of a number of chlorobenzene derivatives have been measured. The frequencies (including additional data from the literature) have been correlated with characteristic parameters, such as Taft's σI and σR. It is found that the Bray–Barnes relation can be somewhat improved by introducing a parameter κ: ν = ν0 + ∑ iκi. The following relations are found: (a) the effects of more than one substituent on the benzene are additive; (b) steric effects (o‐substituents) are not important for the NQR frequencies; (c) a correlation between the NQR frequency ν and Taft's σI and σR (correlation coefficient r = 0.976) shows the importance of the inductive effect on NQR. The mesomeric effect plays only a minor role in 35Cl NQR in benzene derivatives. Unknown σI values may be gained from NQR measurements; for the evaluation of σR, the determination of the chemical shift of 19F NMR seems to be the better method.

Antiferromagnetic spin fluctuations above the dome-shaped and full-gap superconducting states of LaFeAsO1-xFx revealed by (75)As-nuclear quadrupole resonance.

Abstract: We report a systematic study by (75)As nuclear-quadrupole resonance in LaFeAsO(1-x)F(x) The antiferromagnetic spin fluctuation found above the magnetic ordering temperature T(N) = 58 K for x = 003 persists in the regime 004 ≤ x ≤ 008, where superconductivity sets in A dome-shaped x dependence of the superconducting transition temperature T(c) is found, with the highest T(c) = 27 K at x = 006, which is realized under significant antiferromagnetic spin fluctuation With increasing x further, the antiferromagnetic spin fluctuation decreases, and so does T(c) These features resemble closely the cuprates La(2-x)Sr(x)CuO(4) In x = 006, the spin-lattice relaxation rate (1/T(1)) below T(c) decreases exponentially down to 013T(c), which unambiguously indicates that the energy gaps are fully opened The temperature variation of 1/T(1) below T(c) is rendered nonexponential for other x by impurity scattering