Raman spectrum of carbonates MIICO3 in the 1100-1000cm -1 region: observation of the ν1, mode of the isotopic (C16O182O)2- ion

The Raman spectrum of a series of carbonates MIICO3 with aragonite or calcite structure has been reinvestigated in the 1100-1000 cm-1 region, corresponding to the totally symmetric stretch (ν1) of the (CO3)2- anion. Besides the very strong peak corresponding to the ν1 mode of the (C16O3)2- ion, nearly all spectra exhibit a very weak satellite peak whose frequency agrees well with the calculated ν1 frequency of the isotopic ion (C16O182O)-2. Small deviations from the theoretical values are qualitatively discussed on the basis of vibrational couplings between near-neighbour anions. © 1991.