CO BOND MOMENT IN THE CARBONATE ION

Abstract

Varitation of the $C^{12} - C^{13}$ ratio in carbonates of the aragonite lattice leads to fine structure in the 12$\mu$ region whose spacing and qualitative intensity can be fitted satisfactorily by the introduction of a nearest neighbor coupling constant in the potential energy. The coupling constant is believed to arise from dipole-dipole forces. From the coupling constant the value of the CO bond moment is found to be $1.52 \pm 0.1$ debyes in $BaCO_{3}$, $1.56 \pm 0.1$ debyes in $SrCO_{3}$. The coupling is so large in $CaCO_{3}$ (on account of the inverse cube dependence upon interdipole distance) that the perturbation theory cannot be applied without modification.