AN EFFICIENT BROAD-BAND DECOUPLING SEQUENCE FOR LIQUID-CRYSTALS

A new and efficient broadband decoupling sequence is presented. It is based on the phase cycling of two pulses with small phase angles. The pulse width is 180 degrees +/- 30 degrees, and the phase angle is +/-1 0 degrees-12 degrees. The sequence contains 16 elements, and is called SPARC-16 as an abbreviation for small phase angle rapid cycling. The application of this sequence to a liquid crystalline compound, 4-n-pen tyl-4'-cyanobiphenyl (5CB), is reported. The signal-to-noise ratios an d the linewidths of the C-13 peaks of 5CB with SPARC-16 decoupling and with other decoupling methods are compared. The results show that the broadband decoupling efficiency of SPARC-16 is considerably better th an those of other methods. (C) 1998 Academic Press.