The peak intensities within the multiplets in a 2-dimensional NOESY expt. with small flip angles reflect the transition probabilities due to dipolar and other relaxation mechanisms. In the initial rate approxn., the relaxation rates (elements of the W matrix) can be extd. directly from individual peak amplitudes. Beyond the linear regime, a comparison of exptl. and simulated spectra allows one to distinguish between different hypotheses regarding assignment, structure and mol. motion. [on SciFinder (R)]