Non-equilibrium nuclear spin states

Any physical quantum system is in thermal contact with its environment and if left undisturbed, will always come to thermal equilibrium with its surroundings. Nuclear magnetic resonance techniques however displace the system from its thermal equilibrium position. The amount of time a system may be displaced from its thermal equilibrium position is inherently time limited due to constant information exchange between the system and the environment. This fundamental process is known as quantum relaxation or quantum decoherence. In this thesis we focus our attention on the relaxation dynamics of nuclear spin ensembles. Particular spin configurations may display surprisingly long relaxation time constants and surprising dynamical behaviour as the system deviates further from its thermal equilibrium position. A simple framework for the description of nuclear spin systems far from thermal equilibrium is described and its necessity is experimentally demonstrated by consideration of simple model systems. The presented framework aims to advance recent developments in the storage of hyperpolarised materials, which ideally posses exceptionally long relaxation times and highly ordered spin configurations.