Separated local field spectroscopy of columnar and nematic liquid crystals

We are in this work comparing the efficiencies of various H-1-C-13 separated local field (SLF) experiments when applied to columnar and nematic liquid crystals. In particular, the performances of the conventional SLF, proton-detected local field (PDLF), and polarization inversion spin exchange at the magic angle (PISEMA) methods in terms of spectral resolution, robustness, and ability to measure long-range couplings are investigated. The PDLF sequence provides in most cases the best dipolar resolution. This is especially obvious for weakly coupled H-1-C-13 spin pairs. (C) 2003 Elsevier Science (USA). All rights reserved.