Abstract
Abstract X-band and Q-band ESR measurements of Mn(II) ions contained in Japanese cultured marine pearls and pearl oyster (Pinctada fucata) were carried out at room temperature. The ESR spectra observed for the powdered samples of nacreous and prismatic layers revealed the ESR hyperfine structures typical to Mn(II) in an aragonite lattice and a calcite lattice, respectively. The ESR spectra were interpreted with the following spin Hamiltonian. \mathscrH=gβH·S+aS·I–gnβnH·I+D[Sz2–S(S+1)⁄3]+E(Sx2–Sy2) The resonance fields for all the M=+1⁄2↔M=−1⁄2 ESR transitions were derived, with the third-order corrections all taken into account. The zero-field splitting parameters D and E for Mn(II) ions in these biominerals were estimated by computer simulations of the ESR line shapes. The estimated parameters for the nacreous Mn(II) ion (D=20.8 mT, E=6.9 mT) are apparently different from those for the prismatic Mn(II) ion (D=8.5 mT, E=1.4 mT).
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