Chapter 21: Long-lived Spin Order in Methyl Groups

The existence of long-lived nuclear spin states (LLS) in methyl groups was deduced from the observation of unusual hyperpolarised ¹³C and ¹H spectra in dissolution-NMR experiments. The ensuing study of methyl LLS has led to an improved understanding of the role of symmetry, internal motion, and cross-relaxation in the theory and applications of long-lived spin order. Methyl groups being ubiquitous chemical moieties, methyl LLS also could open the prospect of a broader range of applications, but this is counterbalanced by the lack of coherent control on long-lived spin order for systems of equivalent spins.