Study of a spin system by a spin-echo sequence

Abstract

The density matrix describing the evolution of a spin system excited by a spin-echo sequence is calculated from the equilibrium state to the acquisition period by taking into account only the first-order quadrupolar interaction. The formation of an echo due to the two satellite transitions is predicted, and the line intensity of the central transition and a satellite transition of the free induction decay following the second pulse are obtained for any ω_Q/ω_rf ratio. Sodium nuclei in powdered NaNO₃ and lithium nuclei in a single crystal of LiTaO₃ are used to illustrate three experimental conditions: the interpulse delay is smaller, comparable or larger than the duration of the free induction decay.