Methods other than DNP may also produce high nuclear spin polarization, either in thermal equilibrium with the solid lattice, or in dynamic equilibrium in a rotating frame. Optical pumping methods create a very high enhancement of the nuclear spin polarization based on spin exchange collisions with atoms whose outer electron is polarized by circular polarized light. Some methods are also based on creating high non-equilibrium polarization that is then frozen in by increasing the spin–lattice relaxation time. Chemical and biomedical research teams use the term “hyperpolarization” to describe the general methods of spin polarization enhancement beyond thermal equilibrium; DNP methods belong clearly to these. Other methods include optical pumping and chemical polarization methods such as Chemical Induced Dynamic Nuclear Polarization (CIDNP) and Parahydrogen Induced Polarization (PHIP).

The DNP phenomenoma are first overviewed basing on magnetic spin transitions and on thermal reservoirs, before turning to the microscopic and quantum statistical descriptions using the high-temperature approximation. The dynamic cooling of dipolar interactions is then extended to low temperatures and the stationary solution of Borghini is developed. The physical limits of the equal spin temperature model are discussed, focusing on the electron spin concentration, cross relaxation and hyperfine interactions, before treating the limitations arising from the heat transport, diffusion barrier, leakage factor and phonon bottleneck . The resolved and differential solid effect mechanisms are then presented before turning to the cross effect, Overhauser effect and DNP of hyperfine nuclei. The microwave frequency modulation effects are discussed in view of the “hole burning” due to limited cross relaxation and due to uneven power absorption cause by the magnetic dispersion and by inhomogeneity of the magnetic field.