Two-pulse echo in solids containing isolated three-spin systems

Abstract

The response of an isolated three-spin system in solids to the pulse sequence 90°-τ-βφ; is investigated theoretically and experimentally. It is shown that in this system an echo occur both in the case of 90°-τ-90°90° (“solid” echo) and in the case of 90°-τ-β0° pulse sequences. In contrast to the “solid” echo the 90°-τ-β0° echo is observed not at 2τ but is shifted. The value and sign of this shift depend both on τ and on parameters characterising the geometry and orientation of the three-spin system in a magnetic field. The experiments on polycrystalline (CH3)4NBr are in good agreement with theory. [Russian Text Ignored]