POPULATION TRANSFERS FOR NMR OF QUADRUPOLAR SPINS IN SOLIDS

The manipulation of spin-state populations is investigated for quadrup olar nuclei with pulsed and frequency-swept RF fields. The frequency-s weep method is an effective way to interchange the populations of two levels and does not require exact knowledge of the transition frequenc y. Results for allowed (Delta m = 1) and forbidden transitions (Delta m > 1) are reported for Al-27 in a single crystal Al2O3. The behavior of the higher-order transitions establishes a lower limit for the swee p rate for sensitivity enhancement of the central transition for powde rs and amorphous solids. (C) 1994 Academic Press, Inc.