COMPUTATION OF ORIENTATIONAL DISTRIBUTIONS OF PARTIALLY ORDERED SAMPLES FROM NMR-SPECTRA

This paper describes the application of a regularization technique to the determination of the orientational order from the NMR lineshape in partially ordered samples. Different types of NMR spectra are discuss ed, such as C-13 spectra governed by chemical shift and H-2 spectra wi th dominating quadrupolar interactions. For uniaxial interaction tenso rs, the orientational-distribution density function of the sample may be retrieved from the spectra if the tenser principal values are known . The distribution function is approximated by means of linear interpo lation between discrete interpolation nodes. It is computed by solving a Fredholm integral equation of the first kind. Additional relaxation terms may be included in the fitting procedure. The stability of the numerical solutions is tested. An application to nematic liquid crysta ls is shown. (C) 1995 Academic Press, Inc.