Nuclear Magnetic Moments (nuclear + magnetic_moment)

Distribution by Scientific Domains


Selected Abstracts


Nuclear magnetic moments from NMR spectra,Experimental gas phase studies and nuclear shielding calculations

CONCEPTS IN MAGNETIC RESONANCE, Issue 5 2007
Karol Jackowski
Abstract NMR spectra of gaseous compounds and quantum chemical calculations are combined to determine new accurate values of magnetic dipole moments for a series of nuclei. We have analyzed shielding constants, resonance frequencies, and nuclear magnetic moments for a group of simple molecules. The chemical shifts and resonance frequencies are measured at 300 K and extrapolated to the zero-density limit in order to remove all the intermolecular effects from the experimental parameters. The absolute shielding constants in the studied molecules are obtained from ab initio calculations. Assuming the proton magnetic moment as the reference, we determine the nuclear magnetic moments of 13C, 14N, 15N, 17O, 19F, 29Si, 31P, 33S, and 73Ge. The new nuclear magnetic moments are consistent with the experimental NMR parameters, and using these new values one can for the first time predict successfully the shielding constant of a nucleus in a molecule when the corresponding resonance frequency is known. © 2007 Wiley Periodicals, Inc. Concepts Magn Reson Part A 30A: 246,260, 2007. [source]


Metallic Li in carbonaceous nanotubes grown by metalorganic chemical vapor deposition from a metalorganic precursor

APPLIED ORGANOMETALLIC CHEMISTRY, Issue 11 2008
Mahua Das
Abstract Metallic Li in carbonaceous nanostructures was obtained in high concentration (as much as 33.4%) through metalorganic chemical vapor deposition involving certain lithium,aminoalkyl moieties, which are formed in situ, by decomposition of a precursor containing both cobalt and lithium. The bimetallic complex containing both lithium and cobalt was characterized by IR spectroscopy, mass spectroscopy, nuclear magnetic resonance spectroscopy, elemental analysis and thermogravimetric analysis. X-ray photoelectron spectroscopy measurements performed on the as-grown films demonstrate that lithium can be stable in metallic form in such a film. Results of X-ray photoelectron spectroscopic analysis of the as-grown films are presented as direct evidence of the formation and stabilization of metallic lithium in carbon nanotubes. Carbon nanotubes, encapsulating metallic lithium, can potentially act as a miniaturized nanobattery. Such a battery would be potentially useful in the next generation of communication and remote sensing devices, where a pulse of current is required for their operation. In addition, with metallic lithium, having an effective nuclear magnetic moment, such materials can be envisioned to show potential applications in devices based on nuclear magnetic resonances. Copyright © 2008 John Wiley & Sons, Ltd. [source]


Nuclear magnetic moments from NMR spectra,Experimental gas phase studies and nuclear shielding calculations

CONCEPTS IN MAGNETIC RESONANCE, Issue 5 2007
Karol Jackowski
Abstract NMR spectra of gaseous compounds and quantum chemical calculations are combined to determine new accurate values of magnetic dipole moments for a series of nuclei. We have analyzed shielding constants, resonance frequencies, and nuclear magnetic moments for a group of simple molecules. The chemical shifts and resonance frequencies are measured at 300 K and extrapolated to the zero-density limit in order to remove all the intermolecular effects from the experimental parameters. The absolute shielding constants in the studied molecules are obtained from ab initio calculations. Assuming the proton magnetic moment as the reference, we determine the nuclear magnetic moments of 13C, 14N, 15N, 17O, 19F, 29Si, 31P, 33S, and 73Ge. The new nuclear magnetic moments are consistent with the experimental NMR parameters, and using these new values one can for the first time predict successfully the shielding constant of a nucleus in a molecule when the corresponding resonance frequency is known. © 2007 Wiley Periodicals, Inc. Concepts Magn Reson Part A 30A: 246,260, 2007. [source]


Predicted signs of reduced two-bond spin,spin coupling constants (2hKX,Y) across X,H,Y hydrogen bonds

MAGNETIC RESONANCE IN CHEMISTRY, Issue 5 2004
Janet E. Del Bene
Abstract The reduced two-bond Fermi-contact terms and the reduced spin,spin coupling constants 2hKX,Y across X,H,Y hydrogen bonds for complexes stabilized by C,H,N, N,H,N, O,H,N, F,H,N, C,H,O, O,H,O, F,H,O and C,H,F hydrogen bonds are positive. The NMR Triplet Wavefunction Model (NMRTWM) indicates that the signs of the reduced FC terms and 2hKX,Y are determined by excited triplet states that have an odd number of nodes intersecting the X,Y axis between X and Y, thereby leading to an antiparallel alignment of the nuclear magnetic moments of atoms X and Y. Copyright © 2004 John Wiley & Sons, Ltd. [source]