Spatially resolved optical studies of F-center diffusion, during and after photo-thermal F  X color center conversion, were carried out by applying optical scanning and holographic methods to electrolytically colored crystals. The average velocities and diffusion coefficients of F centers were determined for Gaussian and periodic spatial light intensity distributions. A marked effect of the light intensity gradient upon F-center diffusion was detected. This was manifested by a rapid increase in the effective diffusion coefficient when the light intensity gradient was decreased.

O.Salminen, P.Riihola, A.Ozols, T.Viitala: Physical Review B, 1996, 53[10], 6129-36