PARAMAGNETIC CENTERS IN GAMMA-IRRADIATED SYNTHETIC MONOHYDROCALCITE

When spherulitic grains of (CaCO3.H2O)-C-12, C-13 are gamma-irradiated at room temperature, only three isotropic paramagnetic species are produced: 1) the tumbling CO3- radical with g = 2.0115 and A13c = 11.4 gauss; 2) the tumbling CO2- radical with g = 2.0006 and A13c = 148 gauss; and 3) a non-carbon-centered species (SO3-?) with g = 2.0032 exhibiting an hyperfine coupling interaction of 21.2 gauss with two equivalent I = 1/2 nuclei (H). If these rotating species do substitute for the carbonate ion, they are surrounded by a sphere of water molecules. The isotropic CO2-(dating signal) observed in natural carbonates and the CO2-radical in monohydrocalcite have very similar characteristics, suggesting that the first one is also surrounded by water molecules incorporated in the lattice in some ''parasitic'' manner, for example together with Mg2+ or Zn2+ ions.