Polarized i.r. reflection and Raman spectra of sodium formate crystal

Polarized i.r. reflection spectra from the (010) and the (001) planes and polarized Raman spectra for the incident lights propagating along the ′a, the b and the c axes of single crystals of sodium formate were measured. The TO and the LO frequencies were determined for a number of the i.r. active intraionic and lattice modes. In both the i.r. and the Raman spectra, the frequency of the CH in-plane deformation mode ν₅ was proved to be higher than that of the CO₂ symmetric stretching mode ν₂. The TO—LO splittings of the intraionic modes were found to be correlated closely with the corresponding gerade-ungerade splittings and the i.r. absorption intensities.