The Signs of Frequencies and Phases in NMR

The signs of radiofrequency phases and frequencies used in are also fraught with subtle sign problems, for example, NMR are examined carefully. Some fundamental problems with cross-correlated relaxation ( 4‐9) , nuclear demagnetizing current usage are exposed by simple examples. The entire chain of field effects (10‐13) , and phase or frequency shifts induced events leading to the NMR spectrum is examined closely, including by sample movement through nonuniform radiofrequency generation and phase-shifting of the radiofrequency carrier wave, fields (14‐16 ). nuclear-spin dynamics in the presence of the radiofrequency field, There are semantic obstacles to the careful treatment of signs quadrature detection, signal digitization, post-digitization phase in NMR. It is rather striking that scientific English distinguishes shifting, Fourier transformation, and spectral presentation. Rec- between the speed and velocity of linear motion, whereas no ommendations are given for software modifications which should analogous terms exist for the frequency of rotational motion facilitate the correspondence between pulse programming, spectral (J. S. Waugh once tried to remedy this defect by introducing presentation, and spin dynamical theory. q 1997 Academic Press

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