ESR dosimetric properties of modern coral reef

Modern coral reef samples from Egypt were irradiated with (60)Cogamma-rays to study radicals for dosimetric materials with electron spin resonance (ESR). The ESR spectrum for the radical species in unirradiated coral is characterized by four signals with spectroscopic splitting factors of g = 2.0056, 2.0030, 2.0006 and 1.997. The signal at g = 2.0006 +/- 0.0005 is ascribed to free rotation CO2- radicals and used as a dosimetric one. The response to gamma-ray doses ranging from 5 to 10(3) Gy and the thermal stability has been studied. The number of free radicals per 100 eV (G-value) was found to be 0.45 +/- 0.1 and 0.9 +/- 0.18 for coral and alanine, respectively. The lifetime of radicals and the activation energy were estimated from Arrhenius plots to be approximately 8 x 10(5) +/- 1.6 x 10(5) years, and 1.12 eV, respectively. (C) 2003 Elsevier B.V. All rights reserved.