Abstract: Suppression of water peak with pulsed field gradient has been widely used in NMR experiments of biological samples. p selective 90° pulse followed by a z gradient pulse is expected to result in a good suppression.In this paper,the spin dynamics in the presence of gradient field is quantitatively analyzed,and the longitudinal relaxation and the radiation damping effects during the gradient pulsing are discussed.It is shown that high strength and short duration of the gradient are a choice for better water signal suppression.

Key words: Pulsed gradient, Phase randomization dynamics, Longitudinal relaxation, Radiation damping