DYNAMIC POLARIZATION IN CaF, CRYSTALS

Formulae for dynamic polarization in solids having an inhomogeneous electron spin system and a nuclear spin system which can be described by one single spin temperature were derived. It was assumed that the spin temperature, in the rotating frame of those paramagnetic centres which fulfil a)e = a> + a>n or a>e = co — con , can increase due to thermal contact with the nuclear spinsystem brought about by high microwave power. Field fluctuations, at the positions of the paramagnetic centres, due to relaxation flipping of surrounding nuclei and paramagnetic centres were also taken into account. Formulae obtained for the enhancement and polarization time as a function of microwave power and for the enhancement as a function of field modulation frequency and -amplitude agreed well with the experimental results in CaF, single crystals containing H atoms.