ESR and TL investigations on gamma irradiated linden (Tilia vulgaris).

Electron spin resonance (ESR) and thermoluminescence (TL) signals induced by gamma irradiation in linden (Tilia vulgaris) were studied for detection and dosimetric purposes. Before irradiation, linden leaf samples exhibit one singlet ESR signal centred at g = 2.0088. Besides this central signal, in spectra of irradiated linden samples, two weak satellite signals situated about 3 mT left (g = 2.0267) and right (g = 1.9883) were observed. Dose-response curves for the left satellite signal and the central single signal were constructed, and it was found that both of these curves can be described best by the combination of two exponential saturation functions. Variable temperature and fading studies at room temperature showed that the radiation-induced radicals in linden leaf samples are very sensitive to temperature. The stabilities of the left satellite (g = 2.0267) and the central single (g = 2.0088) signal at room temperature over a storage period of 126 days turned out to be best described by a sum of two first-order decay functions. The kinetic features of the left satellite signal were studied over the temperature range of 313-373 K. The results indicate that the isothermal decay curves of the left satellite ESR signal also proved to be best fitted by the combination of two first-order decay functions. Fading and annealing studies suggested the existence of two different radiation-induced free radical species. At the same time, Arrhenius plots evidenced two different kinetic regimes with two different activation energies. TL investigation of polyminerals from the linden samples allowed to discriminate clearly between irradiated and unirradiated samples even 75 days after irradiation.

Dose estimation, kinetics and dating of fossil marine mollusc shells from northwestern part of Turkey.

Electron spin resonance (ESR) spectroscopy was used to determine the geological formation age of fossil mollusc shells taken from marine terrace deposits (Ikizlerçesme-Çanakkale) in northwestern part of Turkey. This work reports the first results obtained by the ESR technique on shells collected from this region. In the ESR spectra of the natural and γ-irradiated shell samples, two different signals attributed to orthorombic (gxx=2.0030, gzz=2.0015, gyy=1.9980) and isotropic (g=2.0006) CO2(-) ion radicals were overlaped (Signal C). Annealing and kinetic experiments suggest the possibility of using the ESR signal at g=2.0015 (C signal) for the estimation of accumulated geological doses. The ESR signal growth curve on additional gamma irradiation has been best fitted by a combination of two single exponential saturation functions. This may support the existence of at least two components of the g=2.0015 ESR dating signal. Based on this model, the accumulated dose of the samples was determined as 110±11Gy. Also the isothermal decay curves of the ESR dating signal could be best described by the combination of two first order decay functions. Activation energy and meanlifetime values at 15°C of the two components were calculated as E1=1.4±0.1eV, E2=1.1±0.1eV, τ1=7.2×10(6) years and τ2=3.3×10(3) years, respectively. Uranium content of the studied shells was found to be high according to their chemical analysis. This may point out that the marine shell has received uranium from outside particularly in carbonate sediment. Therefore, the ESR age of the samples was also calculated using Early Uptake (EU), Linear Uptake (LU) and Combined Uptake (CU) models and results were discussed.