Measurement of the relaxation rates of H-1 longitudinal modes

Accurate decay rate measurements for longitudinal modes are essential for many of the methods proposed for investigating molecular dynamics by NMR. However, the effects of cross relaxation often make it impossible to determine accurate values for these quantities. A method is presented that enables the effects of cross relaxation to be largely eliminated from such measurements. Its reliability is assessed by comparing the values for internuclear distances that can be determined from the resulting relaxation rates with values obtained using other methods. Other consequences of using this technique include an increased robustness of experiments to short (i.e., < 5 T-1) relaxation times and the ability to make multiple ''selective'' relaxation measurements simultaneously. (C) 1997 Academic Press.