Knowledge Bank

Naturally abundant isotopes produce a rich variety of isotopically substituted covalently bound ions in $CaCO3$ (calcite), $NaClO3$, $KClO3$, $NaBrO3$ and $KBrO3$, many of which occur at such low concentrations in the crystal that intermolecular coupling of their vibrations does not occur. These species substitutionally occupy major isotopic species sites and thus are potentially useful probes of the effects of local crystal symmetry on the vibrations of molecular ions. While most of the isotopically substituted ions occur at concentrations too low to permit observation by Raman spectroscopy, spectra of singly $\mathrm{<mrow\; data-mjx-texclass="ORD">17</mrow>}$O and $\mathrm{<mrow\; data-mjx-texclass="ORD">18</mrow>}$O substituted species are reported in this work. Examples are given of isotopic frequencies in agreement with the predictions of a simplified vibrational calculation for the isolated ions. In the case of NaBrO$\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}$ and KBrO$\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}$, evidence is presented which suggests that a single phonon is derived from the totally symmetric stretching vibrations of $\mathrm{<mrow\; data-mjx-texclass="ORD">79</mrow>}$Br$\mathrm{<mrow\; data-mjx-texclass="ORD">16</mrow>}$O$\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow><mrow\; data-mjx-texclass="ORD">-</mrow>}$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">81</mrow>}$Br$\mathrm{<mrow\; data-mjx-texclass="ORD">16</mrow>}$O$\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow><mrow\; data-mjx-texclass="ORD">-</mrow>}$ ions.