Generation and conversion of electronic defects in calcium carbonates by UV/Vis light

Radical species like CO2-, CO3-, SO2-, and SO3- can be created by exposing natural and synthetic calcium carbonates to sunlight or to the light of a H g(Xe) lamp. This poses as a risk for ESR dating of these materials, because the radicals formed by light exposure cannot be distinguished from those g enerated by radioactivity. Furthermore, paramagnetic centers like SO2-, ele ctrons trapped near Zn2+ or Cd2+ ions, surface defects, and radical with g' = 2.0040, can be bleached in gamma-irradiated samples by light and show co nversion effects. (C) 2000 Elsevier Science Ltd. All rights reserved.