CALCULATION OF THE NMR 2ND MOMENT FOR SOLID BENZENE WITH ROTATION ANDDIFFUSION OF MOLECULES - NUMERICAL APPROACH

Numerical calculations of the NMR second moment in case of rotation an d diffusion of molecules were performed. As an example computer simula tions oi molecular reorientation and self-diffusion in solid benzene h ave been performed. For each model and rate of motion the Van Vleck's second moment of the proton NMR absorption spectrum was calculated, an d these values were compared with experimental data. It is concluded t hat restricted self-diffusion must be implied in order to obtain bette r agreement between calculated and experimental NMR second moments. Th e temperature at which self-diffusion was detected through NMR line-wi dth narrowing was found to be about 120 K, nearly 80 K less than the t emperature at which the self-diffusion was detected by T-1 rho relaxat ion measurements.