Recent Development of ESR Dating in Terrestrial Materials

1 Calcium Carbonate (CaC03) Speleothem, Shell and Coral. - 3.1.1 Paramagnetic Impurities Field-swept ESE and Out-of-phase Measurements. Carbonate dissolution and the back reaction of its deposition are described as follows 

Secondary mineral deposits formed by precipitation contain relatively smaller amounts of impurities in the solid (Cs) than that in the liquid (Ci) due to their small distribution coefficient (repulsion coefficient), k = Cs/C. However, both cations such as Mn2+ and Fe3+ and molecular anion impurities such as S032, PO/ and N03 and organic molecules are included in the carbonate. 

The triangular planar (D3h symmetry) CO/ molecular ion with 24 electrons (AB324-type) in CaC03 is easily ionized by radiation to electron and hole centres self-trapped in the lattice or an oxygen vacancy type C02 molecular ion at the anon site. Molecular orbital schemes based on the general scheme of AB3 molecules with 25,24 and 23 electrons for atoms A (B, C, Si, N, P, As and S) and B (O) characterize their specific -factor. Hence, the anisotropic -factor of these radicals estimated from the powder spectrum has been to identify the radical species.1 

Electron centre, C033 (C3 symmetry) A pyramidal AB3-type molecular ion with 25 electrons is stabilized by a trivalent impurity such as Y3+ at room temperature and forms a complex of Y3+ - C033-. The shift of -factors from the free electron value ge = 2.0023 and the hyperfine (hfs) constant, A can be estimated by molecular orbital calculation of AB325 -type molecule  

Hole centre, COT A self trapped hole forms a planar molecule, C03 (D3h symmetry) with 23 electrons (AB323 -type) gives 

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