Multiple-quantum coherences of molecular groups: F-19 in CF3COOAg

The three (3Q) and six (6Q) quantum coherences of two proximate methyl grou ps were studied to find out if they can be used to determine the possible n onequivalence of the groups relative to chemical shifts. Numerical calculat ions of the efficiency of excitation and detection of 3Q and 6Q coherences in reorienting and static methyl group pairs were performed. The crystal or ientation, resonance offset, chemical shifts and finite value of the RF fie ld were taken into account. Experimental F-19 2D NMR spectra were obtained from a single crystal of CF3COOAg. To record 6Q spectra in pure absorption mode in presence of chemical shifts, the data were acquired according to th e hypercomplex method. 3Q spectra of the same sample were recorded in absol ute-value mode.