Results 241 to 250 of about 12,151 (297)
The proton nuclear magnetic shielding tensors in biphenyl: Experiment and theory
Journal of Magnetic Resonance, 2005 Line-narrowing multiple pulse techniques are applied to a spherical sample crystal of biphenyl. The 10 different proton shielding tensors in this compound are determined. The accuracy level for the tensor components is 0.3 ppm. The assignment of the measured tensors to the corresponding proton sites is given careful attention.
Schönborn, F. +6 more
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Parity-violating contributions to nuclear magnetic shielding
Physical Review A, 2003 A gauge-invariant formalism is developed to describe the effect of parity-violating weak-nuclear interactions on nuclear magnetic chemical shift in molecules. Such effect is computed for two molecules with ab initio techniques and it is found to be orders of magnitude smaller than experimental resolution for the molecules considered.
A. SONCINI +2 more
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A REMARK ON THE ISOTOPE SHIFT IN NUCLEAR MAGNETIC SHIELDING
Canadian Journal of Physics, 1964 Isotope shifts in nuclear magnetic shielding have been calculated in the molecular hydrogen system by a semiempirical procedure, which assumes that the high-frequency term varies with internuclear distance R as Rm. It has been found, through a comparison with other investigations, that the choice of m = −1.9 appears to be reasonable. If this choice is
A. Saika, H. Narumi
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Anisotropic Nuclear Magnetic Shielding In C60
, 1991 Extrapolation from ab initio coupled Hartree-Fock calculations is used to estimate the anisotropic C-13 nuclear shielding tensor for each site in C60. The principal components of the symmetric shielding tensor are 179, 10, and -51 ppm. The derived chemical shifts have the same pattern as those deduced from solid-state NMR measurements, and their mean ...
P. W. FOWLER +3 more
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Nuclear Magnetic Shielding in F2
The Journal of Chemical Physics, 1969The 19F chemical shift between gaseous F2 and SiF4 has been measured to be − 596.0 ± 0.2 ppm at 30°C. With a recently established absolute shielding scale for 19F this value yields an absolute shielding in F2 of − 232.6 ppm. Combination of this with the measured spin–rotation constant leads to a separate determination of experimental values for σFd and
David K. Hindermann, Lesley L. Williams
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Nuclear magnetic shielding in cyclopropane and cyclopropenyl cation
Journal of the American Chemical Society, 1983The magnetic shielding tensors of the proton and carbon nuclei have been rationalized by coupled Hartree-Focktheoretical studies. Orbital contributions are systematically analyzed and electron current density maps are shown, indicatingthe typical paramagnetic axial vortex of cyclic molecules.
LAZZERETTI, Paolo, E. ROSSI, R. ZANASI
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Nuclear magnetic shielding of nitrogen in ammonia
The Journal of Chemical Physics, 1991The nitrogen shielding surface in ammonia is calculated using the localized orbital-local origin (LORG) method of Hansen and Bouman, in terms of the symmetry coordinates for the molecule. With respect to the inversion coordinate, the N shielding surface has a shape similar to the potential surface.
Cynthia J. Jameson +2 more
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Nuclear magnetic shielding in boronlike ions
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2017Abstract The relativistic treatment of the nuclear magnetic shielding effect in boronlike ions is presented. The leading-order contribution of the magnetic-dipole hyperfine interaction is calculated. Along with the standard second-order perturbation theory expression, the solutions of the Dirac equation in the presence of magnetic field are employed.
A.M. Volchkova +7 more
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Isotope Effects on Nuclear Magnetic Shielding in Molecular Hydrogen
The Journal of Physical Chemistry A, 2018The secondary isotope shifts of six molecular hydrogen isotopologues (H2, D2, T2, HD, HT, and DT) were measured using gas-phase nuclear magnetic resonance spectroscopy. It was found that these isotope shifts are in satisfying agreement with performed ab initio quantum chemistry computations.
Piotr Garbacz, Grzegorz Łach
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Nuclear Magnetic Shielding for Hydrogen in Selected Isolated Molecules
The Journal of Physical Chemistry A, 2012We present the results of gas-phase NMR measurements designed to yield a new experimental value for the absolute (1)H magnetic shielding for an isolated hydrogen molecule and its deuterium isotopomers. The results are based on the original method of direct shielding measurements (Jackowski et al., 2010) and the density dependence of (1)H, (2)H, and (3 ...
Piotr, Garbacz +3 more
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