The suggested approach allowed us to derive analytical expressions for modeling the shape of solid-echo signal and its time evolution for a system of three-spin groups with arbitrary constants of dipole–dipole interaction (DDI) in solids. Our method is based on the use of symmetry operations for spin exchange and spin flipping along the axis of initial polarization. Most useful seem to be the results on the shape solid echo signals. Upon comparison with experiment, our results may in turn be helpful in estimating a ratio of DDI constants and elucidating the mutual orientation of three-spin groups in a solid under study.

中文翻译：

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具有任意偶极-偶极相互作用常数的三自旋群中的固体回波

建议的方法使我们能够推导出解析表达式，用于模拟固体回波信号的形状及其时间演变，用于固体中具有任意偶极-偶极相互作用 (DDI) 常数的三自旋群系统。我们的方法基于使用对称操作进行沿初始极化轴的自旋交换和自旋翻转。最有用的似乎是形状固体回波信号的结果。通过与实验进行比较，我们的结果反过来可能有助于估计 DDI 常数的比率并阐明所研究固体中三自旋群的相互取向。