THE EFFECT OF BULK MAGNETIC-SUSCEPTIBILITY ON SOLID-STATE NMR-SPECTRAOF PARAMAGNETIC COMPOUNDS

The effect of bulk magnetic susceptibility (BMS) on solid state NMR sp ectra of paramagnetic compounds was investigated theoretically and exp erimentally. The EMS shift was calculated for cylindrical and spherocy linderical containers with some ratios of the length L and the diamete r D. The results show the best resolution can be obtained by using a l ong cylindrical sample container with L/D > 10 and by exciting only th e region near the center of the container. The effect of the random or ientations and distributions of crystallites in a powder sample was al so calculated according to a model proposed by Schwerk et al. [J. Magn . Reson. A 119, 157 (1996)] with removing the Fermi contact term from their model. Static and the magic-angle spinning C-13 NMR spectra were recorded on two paramagnetic compounds of Ln(C2D5SO4). 8H(2)O where L n = Pr, Yb. The modified theory predicts the BMS broadening of the exp erimental spectra very well. (C) 1998 Academic Press.