Intramolecular mode mixing in NaClO3 and NaBrO3

The F symmetry phonons originating in the anion ν1 and ν3 intramolecular vibrations in single crystal NaClO3 and NaBrO3 contain contributions from both kinds of intramolecular motion. This intramolecular mode mixing is described in terms of the intermolecular coupling of vibrationally induced dipoles. The general problem of dipolar coupling in systems in which the intramolecular vibrational polarization directions are not coincident with the crystallographic axes is examined. Finally, the amount of intramolecular mode mixing in NaClO3 and NaBrO3 is calculated and discussed.