Abstract: A paramagnetic center F⁰ was found in thermoluminescent (TL) phosphor LiF:Mg,Cu,irradiated with γ-rays and the g values of its ESR spectrum are g_xx=2.0030, g_yy=2.0450 and g_zz=2.0215 with the splitting values of A_xx=511.04G, A_yy=505.42G, A_zz=507.26G, respectively. The concentration of F⁰ enters decrease with the increase of Mg⁺⁺ concentration. The ENDOR spectrum of the phosphor shows the existance of Cu nuclei near F⁰ enter. The impurity Cu in LiF:Mg,Cu, is in the state of Cu⁺ and its valence did not change directly by γ-irradiation as no ESR signal of Cu⁺⁺ was observed either before or after the irradiation. The axial symmetry ESR signal of Cu⁺⁺ can be found in the ESR spectrum of LiF:Mg,Cu,P before γ-irradiation. After the irradiation the ESR peaks of O^- hole centers and free radicals of PO₃^2- were produced and the environment of Cu⁺⁺ in LiF:Mg,Cu,P phosphor was changed. These results are helpful to explain the function of Cu and P in the thermoluminesence of LiF:Mg,Cu,P.

Key words: Doped LiF, Thermoluminescent (TL) phosphor, γ-irradiation, ESR, ENDOR