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.

Prediction and experimental comparison of deuterium quadrupole coupling constants in some bifluoride salts: An extreme example of symmetric hydrogen bonding in different crystalline environments

Abstract: The electric field gradient (EFG) at the deuterium nucleus of the bifluoride ion, a linear symmetrically H‐bonded system, has been calculated using ab initio Hartree–Fock SCF, singles and doubles CI, and coupled pair functional methods using basis sets ranging from double zeta to the [7,5,2,1;5,4,2] contracted Gaussian set. For the free DF−2 ion, the EFG and the resulting nuclear quadrupole coupling constant (nqcc) are found to be very low and positive in sign, and to display marked dependences on basis set, and the effects of electron correlation and vibrational averaging. In particular, we note a peculiarly extreme basis‐set limit problem for deuterium EFGs in symmetric H‐bonded molecules. The effects of the crystal lattice on the nqcc have been calculated for the sodium, potassium, and ammonium bifluorides taking into account: the direct contribution of the lattice to the EFG as modeled by a point‐charge distribution; its polarizing effect on an individual DF−2 ion using two different methods; and also...

Ab initio study of two quinoline derivatives as corrosion inhibitor in acidic media: electronic structure, inhibitor–metal interaction, and nuclear quadrupole resonance parameters

Abstract: Density functional theory B3LYP and Hartree–Fock methods with 6-311++G** basis set were utilized to study the relationship between electronic structure and corrosion inhibition efficiencies of protonated and non-protonated forms of 3-formyl 8-hydroxy quinoline and 5-naphthylazo-8-hydroxyquinoline (5NA8HQ) in acidic media in gas and solvent phase. Quantum chemical parameters including highest molecular orbital energy, lowest unoccupied molecular orbital energy, energy gap (ΔE g), the fraction of electrons transferred (ΔN), and energy change during charge transfer (ΔE) were calculated. Protonation energy calculations showed that the favorite protonation site of 5NA8HQ is the N12 position, which is confirmed by the result of previously reported experimental investigations. Calculations on the inhibitor/iron system were performed using the B3LYP/6-311++G** method and found that azo nitrogens of 5NA8HQ have better interaction with iron. Also, nuclear quadrupole resonance parameters indicate that azo nitrogens (N11 and N12) are the best sites for interaction with iron.

Evidence for Point Nodes in the Superconducting Gap Function in the Filled Skutterudite Heavy-Fermion Compound PrOs4Sb12: 123Sb-NQR Study under Pressure

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 $\Delta_{\rm CEF}$ between the ground state $\Gamma_1$ singlet and the first excited state $\Gamma_4^{(2)}$ 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 $\Delta(\theta)=\Delta_0\sin\theta$ with $\Delta_0$ = 3.08$k_{\rm B}T_{\rm c}$. The relation between the superconductivity and the quadrupole fluctuations associated with the $\Gamma_4^{(2)}$ state is discussed.