The presence of spinning sidebands can severely compromise pression will not be used, the first criterion is satisfied. the detection of low molarity analytes. Spinning sidebands have Modern NMR spectrometers, appropriately configured, traditionally been minimized by improving the magnetic field hohave the ability to achieve and maintain high quality linemogeneity and by varying the spinning of the sample in a linear shapes given the current state of probe and shim system fashion during data acquisition. The effect of the latter is to spread design and implementation. The control of spinning sidethe spinning sideband intensity over a range of frequencies so that bands is the subject of this article.
the final result is a spinning sideband whose shape reflects the distribution of spinning speeds. We have designed a customized THEORY profile of spinner speed variation that optimizes the reduction of spinning sidebands. The customized profile is based on theoretical
The theory of spinning sidebands has been described by considerations of how the intensity of sidebands vary with the rate of sample rotation and also compensates for the mechanical design Williams and Gutowsky (5), Dadok (6), and Allerhand of the spinner mechanism. The result is a unique combination of and Maple (7). As originally developed by Williams and an exponential increase in gas flow rate to balance the theoretical Gutowsky the theory of spinning sidebands assumed, quite considerations coupled with a strategically placed rapid change in correctly at that time, that spinning sidebands were due priair flow to annul the sluggish response of the spinning mechanism marily to samples spinning in the presence of linear H 0 gradito acceleration. The resulting sideband shape is a broad, flat, ents perpendicular to the axis of rotation. Under these condisquare step in the baseline that is least likely to interfere with low tions, spinning sidebands are observed whose relative intemolarity analyte peaks. α§ 1998 Academic Press grated intensities are given by A {n (k) Γ
J 2 n (k) 0 J n 01 (k)J n /1 (k), [1]