Nuclear Spin Alignment and Relaxation

Nuclear spin alignment and relaxation describe how nuclear spins respond to a magnetic field and then return to equilibrium. Without an external magnetic field, nuclear spin states are degenerate, meaning they have the same energy, and the spins are randomly oriented.

When a magnetic field is app...

When degenerate nuclear spin states align with or against an applied magnetic field as per Boltzmann's distribution, their magnetic moments precess around the z axis.

Recall that the excess population in the lower energy state results in a net magnetization, M, along the z axis, with no net contribution from the transver...