Relaxation mechanisms
Nuclear magnetic resonance

In most cases, relaxation results from the interaction between a core's magnetic moment and a fluctuating local magnetic field B_L(t).

Longitudinal (or spin-lattice) relaxation concerns the M_z component of magnetization. It is associated with an energy transfer with the lattice, a term that designates the entire environment of the nucleus under consideration. The fluctuating magnetic field B_L(t) has a role analogous to that of the coherent radio-frequency field B₁ if the range of frequencies associated with the B_x, B_y components of B_L(t) satisfies the resonance condition for the type of nucleus under study. It then causes a nuclear spin transition. It should be noted that B_L(t), an incoherent field, cannot create coherences.