FIELD-SWEPT NMR-SPECTRA OF B-11 IN PYREX GLASS AND NB-93 IN NBN PERTURBED BY QUADRUPOLE INTERACTION

NMR experiments of B-11 by both field-swept and high-resolution NMR ar e reported to probe the electric field gradient at boron sites and its distribution in Pyrex glass. Both spectra are successfully interprete d with the same set of parameters. It is stressed that field-swept NMR experiments to observe total powder spectrum can be helpful to get in formation on electric field gradients and asymmetry parameters if ther e exist many nonequivalent sites of atoms, since satellite transitions are affected by the larger first-order quadrupole effect. Field-swept NMR of Nb-93 in superconducting NbN powder, prepared by self-propagat ing high-temperature synthesis, is also reported. A very broad field-s wept spectrum disturbed by quadrupole interaction has been observed. T he spectrum is simulated by assuming distributions in electric field g radient and Knight shift at Nb sites. It is stressed that a combinatio n of experiments at separated frequencies is important.