Resurrection of Crushed Magnetization and Chaotic Dynamics in Solution NMR Spectroscopy

摘要

We show experimentally and theoretically that two readily observed effects in solution nuclear magnetic resonance (NMR)—radiation damping and the dipolar field—combine to generate bizarre spin dynamics (including chaotic evolution) even with extraordinarily simple sequences. For example, seemingly insignificant residual magnetization after a crusher gradient triggers exponential regrowth of the magnetization, followed by aperiodic turbulent spin motion. The estimated Lyapunov exponent suggests the onset of spatial-temporal chaos and the existence of chaotic attractors. This effect leads to highly irreproducible experimental decays that amplify minor nonuniformities such as temperature gradients. Imaging applications and consequences for other NMR studies are discussed.