Triple quantum NMR on spin systems with I = 3/2 in solids

Abstract

Pulsed NMR experiments are developed for the excitation and the detection of triple quantum coherences in quadrupolar spin systems with I = 3/2. Two experimental methods are used: For systems with small quadrupolar frequencies direct triple quantum excitation and detection is accomplished by weak rf irradiation pulses. For large quadrupolar frequencies modulated rf pulses are applied to create and to monitor triple quantum coherences. Modulated rf pulse techniques are also used to search for quadrupolar frequencies and to excite selectively center frequency spectral lines of I = 3/2 nuclei. Applications of these techniques are demonstrated by 23Na(I = 3/2) NMR experiments on an oriented single crystal of sodium ammonium tartarate tetrahydrate.