Optical absorption and thermoluminescence in LiF TLD-100

Abstract

The thermoluminescent (TL) properties of many LiF samples have demonstrated a strong influence on trace impurities and impurity content on the TL process. Hence, the general validity of any particular model must be tested against its applicability in a standard material such as Harshaw LiF (TLD-100). In this paper the validity of the use of Harshaw LiF(54) by Mayhugh et al. in their model development for the TL process in LiF is demonstrated by comparing the TL and optical properties of LiF(54) with TLD-100. The specific properties of optical absorption bands at 310 and 380 nm, the F band near 250 nm, and the Z3 band near 225 nm are intercompared with observed TL peaks in both materials. Both the gamma and uv-exposure behavior of the Z3 center demonstrates a direct relationship between Z3 and TL peak 10, while no direct conversion between Z3 and the 310-nm band is observed in TLD-100. These results do not support recent models identifying Z3 with TL peak 6 and Z2 with the 310-nm band (and TL peak 5); this is probably due to differences in purity and defect state in the LiF samples used by other investigators, emphasizing the need for standardization of materials in this system.