(544i) Dynamic Molecular Modes to Interpret NMR Relaxation at High Frequencies: Theory and Applications

Nuclear magnetic resonance (NMR) relaxation is a powerful technique for probing matter non-destructively, with applications spanning medicine to material science to petrophysics. At high NMR frequencies, quantum effects are usually negligible, and a semi-classical statistical mechanical description is sufficient to model relaxation. Traditional theories of NMR relaxation assume the relaxation autocorrelation function is mono-exponential, but calculated relaxation evinces a rich, multi-exponential behavior. In this work, we develop an approach to model and interpret this multi-exponential behavior. Drawing inspiration from the idea of inherent structures in liquids, we find that there are dynamic molecular modes that the system samples, with each mode following a mono-exponential decay. In this talk we will present this idea using simple, physical models within a rigorous statistical mechanical development. The key point is that based on the dynamic molecular modes, our statistical mechanical description can predict such multi-exponential decay accurately. These molecular modes contain important information about the structure/dynamics of the system.