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

Radical species like CO−2,CO−3, SO−2, and SO−3 can be created by exposing natural and synthetic calcium carbonates to sunlight or to the light of a Hg(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 generated by radioactivity. Furthermore, paramagnetic centers like SO−2, electrons trapped near Zn2+ or Cd2+ ions, surface defects, and radicals with g′=2.0040, can be bleached in γ-irradiated samples by light and show conversion effects.