Data from three-pulse NMR experiments, namely, the Goldman-Shen pulse sequence and the stimulated-echo sequence, on partially crystallized poly(ethylene glycol) and tetrafunctional dimethylsiloxane networks are presented. A dipole echo has been observed after a third radiofrequency pulse. Quantum mechanical calculations of the response of the spin system to the three-pulse sequences have been performed, considering only thez-zcomponent of the dipole-dipole spin coupling. The resulting expression suggests dipole-echo formation and is in agreement with experimental data.
Bibliographical noteFunding Information:
During the course of this work, we have benefited from discussions with Dr. N. Fatkullin, N. Dautova, and S. Stapf. We are also thankful to M. Litvinov for putting the samples at our disposal. The work has been supported by the Russian Fundamental Investigation Foundation under Project 94-03-09346A.