ABSTRACT
This chapter discusses nuclear spin relaxation, a subclass of the larger subject, in a qualitative way as well as pulse Nuclear Magnetic Resonance methods for measuring them. If an unpaired electron is causing the nuclear relaxation, this is called paramagnetic relaxation, an ambiguous terminology since all nuclei with spins as well as electrons are paramagnetic. If the nucleus has an electric quadrupole moment, it can interact with a randomly varying electric field gradient in the molecule and the process is quadrupolar relaxation. The spin-lattice relaxation time can be viewed as a lifetime of an average chemically equivalent spin in the system. The spin-lattice relaxation rates are for a single pair of protons. The lattice vibrations in solids are not very effective in causing relaxation through the nuclear dipole-dipole interaction mainly because the vibration frequency is so much higher than the usual Larmor frequencies.
