In order to determine dissociation energy of the 1.014 eV photoluminescence (PL) Cu center in silicon crystal, decay of the PL intensity of the center by annealing samples at various temperatures was measured. The samples were prepared by contamination of Cu from Cu solution and heat treatment at 700 °C followed by rapid cooling to room temperature. From the temperature dependence of the time constant of the decay of the PL center, activation energy of dissociation of the center was obtained. The value was 0.47+±0.05 eV, which was much smaller than that (1.02 eV) obtained by the decay of the deep level transient spectroscopy Cu center peak atEv+0.09eV. The present value could reasonably explain the rapid thermalization of rearrangement of the centers after the release of stress which had been observed earlier. ©1998 American Institute of Physics.