STMAS, inverse

In STARTMAS, SQ STs of order q (with q = 2 and p = —1) are initially excited as in STMAS (Fig. 14). The ST coherences then evolve during the first time period r/[2(l + k)], before being converted to a DQ transition by a selective n inversion pulse on the CT (as in DQF-STMAS [161]) and allowed to evolve during kx/(l + k). A second selective n pulse brings the system back to an SQ transition for the last part of the ST evolution. At time t = x, the phase of the detected SQ ST coherence is thus... 

In this review, we shall introduce some basic concepts about sohd-state NMR of half-integer quadrupolar nuclei and discuss the most useful and promising methods presently available to study them. These include older methods, such as Double Rotation (DOR) and Dynamic Angle Spinning (DAS), and novel techniques including MQMAS, Quadrupolar Phase Adjusted Spinning Sidebands QPASS, SateUite Transition (ST) MAS and Inverse-STMAS NMR, and Fast Amplitude Modulation (FAM). We also discuss several techniques based on dipolar interactions between quadrupolar and spin-1/2 nuclei, such as Cross-Polarization (CP) MQMAS, MQ Heteronuclear Correlation Spectroscopy... 

Rocha et al. have reviewed recent advances in NMR spectroscopy of quadrupolar nuclei with half-integer spins. In particular, B, O, Na, A1, Ga, Nb MQ MAS applications have been considered. A range of related techniques, such as satellite transition (ST) MAS, inverse-STMAS NMR, fast amplitude modulation, and techniques based on the dipolar interactions between quadrupolar and spin-1/2 nuclei (CP MQ MAS and MQ HETCOR) and the recently introduced /-coupling based experiments (/-HMQC), have also been reviewed. 

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