Relaxation in NMR Spectroscopy

Abstract

This chapter discusses the foundations of relaxation theory starting from a phenomenological description going to a semi-classical and finally to a quantum-mechanical description. Since the majority of relaxation work in NMR is based on semi-classical relaxation theory (mostly Redfield theory), the emphasis is put on this type of description. Besides the derivation, relaxation pathways in the simple example of a heteronuclear and a homonuclear two-spin system are discussed for dipolar-coupling and chemical-shielding anisotropy-based relaxation including cross-correlated relaxation pathways. Finally, the basics of relaxation in quadrupolar spin systems is briefly discussed.