Transient C-13-H-1 nuclear Overhauser effect in liquid crystal

Significant transient C-13-H-1 nuclear Overhauser effect (NOE) is observed in liquid crystal, and is explained by a local C-13-H-1 dipole-dipole inter action and relaxation. Solomon's classical two-pulse experiment gives a sig nificant maximum in signal intensity of 2.5 times the equilibrium magnetiza tion, and also gives a way of estimating zero-quantum transition probabilit y for a dipole-coupled C-13-H-1 pair. The conventional inversion recovery s equence is recommended for the experimental determination of C-13 spin-latt ice relaxation rates. Magnetization recovery after the Hartmann-Hahn signal enhancement deviates strongly from exponential behavior. Experimental data are shown for an antiferroelectric chiral smectic liquid crystal MHPOBC.