The shapes of NMR absorption lines, free induction decays, and Jeener echoes in systems such as lyotropic liquid crystals have been investigated theoretically and experimentally. For a system having an axis of symmetry for the molecular motion which makes an angle Vthgr; with the external magnetic field, the secular part of the dipolar Hamiltonian ⟨Hd⟩ (Vthgr;) is proportional to (1/2)(3 cos2Vthgr;−1). This leads to the characteristic logarithmic absorption line shape for nonoriented systems. The experimental consequences are illustrated with measurements on nonoriented samples of potassium palmitate–water in the lamellar liquid crystal phase.
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