Pulsed-gradient spin-echo measurements of anisotropic diffusion by dipole-decoupled 13C nuclear magnetic resonance.
A new approach for monitoring diffusion in anisotropic phases is proposed and demonstrated. The method relies on the observation of dilute spins (e.g., 13C) in the presence of heteronuclear high-power dipolar decoupling, a procedure which can yield time-domain nuclear magnetic resonance (NMR) signals lasting over three orders of magnitude longer than their 1H counterparts. This allows one to apply conventional 90-180 degrees pulsed-gradient spin-echo (PGSE) schemes on organic systems without having to employ complex and highly sensitive multiple-pulse 1H irradiation schemes. Instrumental aspects of this 13C method are discussed, and an application to the variable-temperature determination of anisotropic self-diffusion in a thermotropic liquid crystal is illustrated.
Zhou
M
M
Department of Chemistry, M/C 111, University of Illinois at Chicago 60607, USA.
Frydman
L
L
D016880:Anisotropy; D002247:Carbon Isotopes; D004058:Diffusion; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D015203:Reproducibility of Results
D002247:Carbon Isotopes