Dipolar broadening and exchange narrowing of EPR lines from the paramagnetic centers distributed on a solid surface

Experiments with char samples provide support for the theory of EPR line shape in a system of surface paramagnetic centers with dipole-dipole interactions. It is also demonstrated that, if a strong Heisenberg exchange dominates over the dipole-dipole interactions, the EPR line of a two-dimensional system narrows and acquires Lorentzian shape, similar to the three-dimensional case. (C) 2000 MAIK Nauka/Interperiodica.