EPR and TL studies of phenakite crystal and application to dating

Natural crystals of phenakite were investigated concerning the radiation effects on TL and EPR properties and their application for dating. TL peaks at 120, 180, 290 and 440 °C were observed, with one TL emission band around 400 nm. Activation energies and frequency factors obtained by the technique of varying the heating rate indicate lifetimes of 202 × 103 and 714 × 109 years (at 15 °C) of for 290 and 440 °C peaks, respectively. The additive method applied to these two peaks yielded accumulated dose Dac of (1.12 ± 0.09) and (1.39 ± 0.14) kGy. EPR signals of [PO4/e]0 and [SiO4/h]+ centers were observed. The intensity of these centers increase with γ-radiation and the additive method for these EPR centers yielded Dac of (0.27 ± 0.01) and (0.91 ± 0.06) kGy, respectively. Using U, Th and K contents plus the cosmic-ray contribution, a dose rate of 1.52 mGy/year has been obtained. The final ages and stability of these TL and EPR centers under exposure to UV light are discussed.