ABSTRACT
This chapter explores the basis and practical consequences of relaxation for the nuclear magnetic resonance spectroscopy (NMR) experiment. It highlights that NMR is different from most other forms of spectroscopy in that relaxation of nuclear-spin-excited states usually takes place on a much longer time scale than is typical in optical spectroscopy. Besides the slow approach to equilibrium, slow relaxation in NMR is also related to the fact that under most circumstances the rates of the actual relaxation events (spin flips) are not very fast, at least when compared with other spectroscopic methods. The chapter considers what causes spin flips to occur and what effects are important in determining the rate at which they do. The effects of D-coupling are still observed in solution in the form of cross-relaxation and a phenomenon known as the nuclear Overhauser effect (NOE).
