Investigation on optical properties in the surface of KClxBr1-x mixed crystals irradiated to gamma radiation (A new approach)

Background: Similar to the thermoluminescence (TL) spectra, the optical parameters variations can also be used in TL crystals for dosimetry purposes. These optical parameters can include absorption, transmission and reflection coefficients. Materials and Methods: Single crystals of KBr and KCl which have been used in this research were grown from laboratory grade extra pure precursor powders. Crystal growth was performed by using a Czochralski crystal growth apparatus. The grown crystals were irradiated using a 60Co source to doses of 0.5, 1.0 and 1.5 kGy. Reflection spectra were measured by a Shimatzu UVPC 3101 model spectrometer in 5 and 45 incident degree angles. Results: Optical properties of KClxBr1-x mixed crystals surfaces irradiated with gamma radiation were determined. Refraction indices and dielectric coefficients of the crystals in the optical region of 250-750 nm were studied. It was observed that both irradiated and non-irradiated mixed crystals had similar surface behaviour in the order of n ≈ 1.4 and ε ≈ 2.2 in the whole range of 250-750 nm, while colour intensities of irradiated samples were different for various irradiation doses. The reason could have been due to the permanent heat transfer effects with the outer surface layers of the crystal and the rapid relaxation of the excited states in defected surface of the crystal. Conclusion: Reflection spectra along with the crystal surface optical parameters could not be efficient for the dosimetry purposes and additional information such as absorption or transmission data would also be necessary Iran. J. Radiat. Res., 2009 7 (3): 165-169