Transverse nuclear spin relaxation due to director fluctuations in liquid crystals. III. A slow-motional theory for the angular dependence in pulsed experiments

In the previous article, we have proposed a slow-motional theory for second-order effects of director fluctuations on transverse spin relaxation of quadrupolar nuclei in liquid crystals [D. Frezzato, G.J. Moro, and G. Kothe, J. Chem. Phys. 119, 6931 (2003), preceding paper]. This methodology is now generalized to arbitrary orientations of director and magnetic field. The characteristic functions are evaluated for the free induction decay and the echo intensities in Carr-Purcell-Meiboom-Gill (CPMG) multipulse sequences. From the solution of the corresponding integral equations, the relative magnitude of first and second-order contributions can be assessed. This enables a complete characterization of the angular and pulse spacing dependent transverse relaxation rates observed in CPMG multipulse experiments. (C) 2003 American Institute of Physics.