Multiple quantum magic-angle spinning NMR with cross-polarization: Spectral editing of high-resolution spectra of half-integer quadrupolar nuclei

n experiment is presented that combines the techniques of multiple-quantum magic-angle spinning (MQMAS) and cross-polarization (CP) between spin-1/2 and half-integer quadrupolar spin nuclei. This technique, referred to as CP MQMAS, allows the coordination of the spin-1/2 nuclei within a quadrupole system to be determined, which demonstrates its usefulness for spectral editing. The radio-frequency (rf) pulse sequences and necessary phase-cycling are developed and examined. A novel approach of incorporating a 'z-filter' between the two techniques allowed us to optimize our new procedure, CP MQMAS, as two unique experiments prior to their coupling. Experimental details concerning the manipulations necessary to produce and detect multiple-quantum (MQ) NMR spectra of half-integer quadrupole nuclei are presented. Additionally, the spin dynamics of CP from a spin-1/2 nucleus to the central transition of a quadrupolar nucleus during magic-angle spinning (MAS) are examined. For quadrupolar systems the CP process operates most efficiently using very low rf field strengths, which is markedly different than that used in conventional CP between spin-1/2 nuclei. When low rf field strengths are used, no longer can the Hamiltonians from the second-order quadrupolar interaction, MAS speed and carrier frequency(s) offset be treated as negligible. Finally, as the MQMAS technique requires very high rf field strengths, and CP very low rf field strengths, it can be seen that the CP MQMAS technique demands high-quality linear power amplifiers.;As a preliminary test of the CP MQMAS experiment, we chose ;Our second CP MQMAS experiment was accomplished using...