SOLID-STATE NMR IMAGING BY TETRAHEDRAL-MAGIC-ECHO TIME-SUSPENSION SEQUENCES

A new approach to solid-state imaging using tetrahedral magic echoes ( TME) is proposed and compared with the previously reported modified-ma gic-echo (MME) approaches. The comparison has shown that for common or ganic solids, where the homonuclear H-1-H-1 dipolar interaction is dom inant, the degree of TME line narrowing is nearly the same as that of time-suspended MME line narrowing; however, the TME narrowing is subst antially superior to the MME narrowing for solids where the heteronucl ear dipolar interaction between H-1 and a second spin species is compa rable in magnitude to the homonuclear H-1-H-1 dipolar interaction. Thi s superiority stems from the fact that the homonuclear and hereronucle ar interactions do not commute with each other. The TME approach furth er possesses certain practical advantages over the MME approaches. For example, the optional application of gradient pulses during the RF ir radiation periods in the TME sequences increases the scaling factor of the gradient amplitude from 1/4 to 1/2, making the gradient switching easier. No apparent deterioration of the TME line-narrowing by the op tional gradient application was noted. (C) 1996 Academic Press, Inc.