ABSTRACT
Relaxation measurements have found widespread use in many different areas within the fields of physics, chemistry, and biology. There are not many methods available by which dynamics on the timescale afforded by nuclear spin relaxation can be studied, and needless to say, many of the advances within the field of relaxation have therefore been focused on the reliable determination of molecular dynamic parameters. This chapter examines the effect of motions on relaxation and how this can be used to investigate molecular dynamics in systems of various levels of complexity. The fundamental molecular dynamic quantities of primary interest for Nuclear magnetic resonance are time correlation functions for rank-two spherical harmonics of the pair of angles specifying the direction of a given molecule-fixed axis with respect to the laboratory frame. The motional anisotropy is thus related to the strength of intermolecular interactions.
