Temperature Dependence of Nuclear Quadrupole Resonance in Cuprous Oxide

Wijn, H. W. de; Wildt, J.

doi:10.1103/physrev.150.200

Cited by 35 publications

(16 citation statements)

References 8 publications

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“…From the values of y, " in Table 2, one predicts that dq+/dR should be positive, as is observed in most experimental cases, i.e., an increase in q with vibrational quantum number. The situation is quite different at the halogen ion, as emphasized by d e Wijn (8). The values of y, -in Table 3 predict that dq-/dl?…”

Section: Interpretation Of Field Gradients Q' (R) Alkali Field Gradientmentioning

confidence: 90%

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Electric Field Gradients in Alkali Halide Molecules

Laplante¹,

Bandrauk²

1974

Can. J. Chem.

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. Can. J. Chem. 52,2143Chem. 52, (1974. The electric field gradient q has been calculated from Hartree-Fock wavefunctions for the molecules LiF, LiCI, LiBr, NaF, NaCI, NaBr, KF, and KCI. It is found that o and TC electrons behave quite differently. Exchange distortions are of great importance for a proper understanding of o contributions to q. Polarizations of n electrons into the bonding region are also considerable. These effects are responsible for failures of classical models and are further discussed using calculated density difference diagrams. Chem. 52, 2143Chem. 52, (1974. Le present article rapporte les resultats de calculs ab irzitio du gradient de champ electrique y pour la strie de molecules ioniques-type LiF, LiCI, LiBr, NaF, NaCI, NaBr, K F et KCI. Ces gradients ont ete obtenus a I'aide de fonction d'onde de type Hartree-Fock. Ces rksultats demontrent clairement que les electrons o et TC se comportent d'une facon tres differente dans ces molecules. Les distorsions d'echange presentes se rtvelent aussi d'importance lnajeure pour une comprihension adequate de la contribution des electrons o a la valeur de q. La polarisation des electrons n dans la region de liaison est a~~s s i considerable. L'ensemble de ces effets s'avere donc responsable de la faillite des modeles classiques pour I'interpretation de q. La disc~~ssion est appuyee des diagrammes de difference de densite correspondants. IntroductisnThe theoretical interpretation of the electric field gradient q in a molecule is of interest as it is a direct measure of the charge distribution. This follows from the fact that the interaction e2qQ, called the quadrupole coupling constant, between a nuclear quadrupole moment Q and the field gradient q of a molecular charge distribution p, is a weak interaction such that first-order perturbation theory is adequate (1). Experimentally eZgQ is determined from various hyperfine structures in resonance experiments of the microwave type (l,2). The field gradient q is also an intrinsic part of the theoretical expression for the force constant of a diatomic molecule (3).In this article we examine various models used to interpret q in ionic molecules, in particular, the alkali halides. Considerable theoretical work (4) has been done using a simple model based on ions with polarizable charge distributions. The problem then becomes the perturbation of an ion with a nuclear quadrupole moment by the field of an external point charge. The expression for the field gradient of simple ions with closed-shells configurations appears as 'NRCC Postgraduate Fellow. where superscripts f indicate positive and negative ions correspondingly. The factor y,' represents the effect of the deformation of the closed shells of the ion by the external charge on the value of q. If the distorted electron distribution opposes the field gradient of the external charge, then ymi is positive and there is a skieldingeffect, while if the distorted distribution enhances the field gradient, then y , ' is negative and there is an antishieldin...

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Section: Interpretation Of Field Gradients Q' (R) Alkali Field Gradientmentioning

confidence: 90%

“…The introduction of overlap (7) improved the model somewhat but not enough at the halogen. De Wijn (8) which is then used to calculate q-. The values of q+ predicted by de Wijn are also reported in Table 1 and are seen to improve the Sternheimer values of q+.…”

Section: Introductisnmentioning

confidence: 99%

Electric Field Gradients in Alkali Halide Molecules

Laplante¹,

Bandrauk²

1974

Can. J. Chem.

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“…Reyes et al presented an analytical formula 15) to express 63 Q as a function of P up to 2 GPa and T between 4 and 300 K, by combining the T-dependence due to thermally activated phonons 16) and the linear P-dependence, 119 Sn-NMR spectra of metallic tin at 4.2 K. Since the -Sn has a tetragonal crystal structure, the NMR spectrum is broadened by uniaxial anisotropy. The peak represents the Knight shift for the field in the ab-plane.…”

Section: Nmr/nqr Experiments and Ruby Fluorescencementioning

confidence: 99%

Space Efficient Opposed-Anvil High-Pressure Cell and Its Application to Optical and NMR Measurements up to 9 GPa

et al. 2010

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We have developed a new type of opposed-anvil high pressure cell with substantially improved space efficiency. The clamp cell and the gasket are made of non-magnetic Ni-Cr-Al alloy. Non-magnetic tungsten carbide (NMWC) is used for the anvils. The assembled cell with the dimension 29 mm Â 41 mm is capable of generating pressure up to 9 GPa over a relatively large volume of 7 mm 3 . Our cell is particularly suitable for those experiments which require large sample space to achieve good signal-to-noise ratio, such as the nuclear magnetic resonance (NMR) experiment. Argon is used as the pressure transmitting medium to obtain good hydrostaticity. The pressure was calibrated in situ by measuring the fluorescence from ruby through a transparent moissanite (6H-SiC) window. We have measured the pressure and temperature dependences of the 63 Cu nuclear-quadrupole-resonance (NQR) frequency of Cu 2 O, the in-plane Knight shift of metallic tin, and the Knight shift of platinum. These quantities can be used as reliable manometers to determine the pressure values in situ during the NMR/NQR experiments up to 9 GPa.

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“…[11][12][13][14] This makes the amount of Cu 2 O samples inside the cell with the volume of the order of 10 −3 ml at low temperatures. [11][12][13][14] This makes the amount of Cu 2 O samples inside the cell with the volume of the order of 10 −3 ml at low temperatures.…”

Section: Introductionmentioning

confidence: 99%

Manometer extension for high pressure measurement: Nuclear quadrupole resonance study of Cu2O with a modified Bridgman anvil cell up to 10 GPa

Fukazawa

Yamatoji

Kohori

et al. 2007

Review of Scientific Instruments

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We report (63)Cu nuclear quadrupole resonance (NQR) measurement of Cu(2)O under pressure up to about 10 GPa at low temperatures. Because the lattice parameter of Cu(2)O changes with increasing pressure, the electric field gradient at the Cu site also changes correspondingly with pressure. This enables us to use the Cu(2)O as an in situ manometer for high pressure nuclear magnetic resonance/NQR up to about 9 GPa.

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Temperature Dependence of Nuclear Quadrupole Resonance in Cuprous Oxide

Cited by 35 publications

References 8 publications

Electric Field Gradients in Alkali Halide Molecules

Electric Field Gradients in Alkali Halide Molecules

Space Efficient Opposed-Anvil High-Pressure Cell and Its Application to Optical and NMR Measurements up to 9 GPa

Manometer extension for high pressure measurement: Nuclear quadrupole resonance study of Cu2O with a modified Bridgman anvil cell up to 10 GPa

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