Monday, January 14, 2008

CMR - Concepts in Magnetic Resonance - up to Volume 30A Issue 6 - November 2007 (309-393)

Concepts in Magnetic Resonance - up to Volume 30A Issue 6 - November 2007 (309-393)

Concepts in Magnetic Resonance Part A
Volume 30A, Issue 6 , Pages 309 - 348
Published Online: 27 Nov 2007

NMR and the uncertainty principle: How to and how not to interpret homogeneous line broadening and pulse nonselectivity. I. The fundamentals
Csaba Szántay Jr. *
*Correspondence to Csaba szántay Jr., Spectroscopic Research Division, Gedeon Richter Plc., H-1475 Budapest, 10, POB 27, Hungary

Dedicated to Prof. Csaba Szántay Sr. on the occasion of his 80th birthday

uncertainty principle • Fourier transform • NMR lineshape • excitation profile • harmonic phasor

Both the essence of homogeneous NMR line broadening as well as the fact that a short monochromatic radiofrequency pulse exhibits a polychromatic spectral bandwidth and is consequently associated with a broad off-resonance NMR excitation band are often rationalized in terms of a superficial and/or misguided use of the Uncertainty Principle. The problem is of quite fundamental nature, and stems from several deeper issues that reach beyond the world of NMR. To explore this topic, we need to go back to some basic concepts including the Fourier transform, time-frequency analysis, different versions of the uncertainty principle, and linear systems theory. My theme will be developed in four subsequent articles. First, by employing an approach that is unconventional in its thematic structure and applied nomenclature, I present an overview of some basic ideas (periodicity, basis functions, harmonic waves, density functions, etc.) that will then pave the way to discussing, in a somewhat avant-garde manner, the Fourier transform in Part II. © 2007 Wiley Periodicals, Inc. Concepts Magn Reson Part A 30A: 309-348, 2007.
Received: 20 February 2007; Accepted: 14 August 2007

Digital Object Identifier (DOI) - 10.1002/cmr.a.20098

Concepts in Magnetic Resonance Part A
Volume 30A, Issue 5 , Pages 246 - 260
Published Online: 4 Sep 2007

Nuclear magnetic moments from NMR spectra - Experimental gas phase studies and nuclear shielding calculations
Karol Jackowski 1 *, Micha Jaszuski 2
*Correspondence to Karol Jackowski, Laboratory of NMR Spectroscopy, Faculty of Chemistry, University of Warsaw, 02-093 Warszawa, Poland

nuclear magnetic dipole moments • NMR in gases • shielding constants • ab initio calculations

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. Concepts Magn Reson Part A 30A: 246-260, 2007.
Received: 15 January 2007; Revised: 5 June 2007; Accepted: 8 June 2007

Digital Object Identifier (DOI) - 10.1002/cmr.a.20091

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