Here we report the electron migration by photo- or thermostimulation inBaFCl:Eu2+. Electrons released fromFcenters may be trapped by other defect sites to formFaggregates or another type ofFcenter and vice versa. This migration reduces the photostimulated luminescence efficiency, lowers the imaging plate sensitivity, and causes the difference between the optical absorption and photostimulation spectra of color centers. ©1997 American Institute of Physics.