The dynamic nuclear polarization process

The process of dynamic nuclear polarization (DNP) can be qualitatively understood by a simple heat contact between bodies of different heat capacities. These bodies are identified with the three thermal reservoirs corresponding to the electron Zeeman, the electron dipole–dipole and the nuclear Zeeman interaction. The primary cooling process itself, which consists of an off-resonance irradiation of the electron Zeeman reservoir, may be interpreted as a continuous and thus non-adiabatic demagnetization in the rotating frame of reference. In order to maximize the nuclear polarization in the case, when all three bodies are in contact with each other (EST model), it is immediately seen that the heat capacity of the electron dipolar reservoir has to be minimized. Furthermore, this graphical description is very helpful in illustrating, how the completely different approach to the DNP process, the solid effect model, can be implemented into the spin temperature theory.