Abstract
Raman spectra of oriented single crystals of NaBF~4~ were measured at 77 and 298 K. The number of bands and the intensities were in excellent agreement with the unit cell group predictions for the known crystal structure, D, Z = 2. The results for the Ξ½~1~, Ξ½~2~ and Ξ½~4~ regions were in excellent agreement with those of Bates [J. Chem. Phys. 55, 489 (1971)]. A recent study by Rajakumar et al. [J. Raman Spectrosc. 23, 75 (1992)] is erroneous. The new measurements permitted the assignment for the Raman bands in the Ξ½~3~ region. Peaks in the external mode region were very weak because both the Na^+^ and BF~4~^β^ ions have spherical symmetry, small polarizabilities and small polarizability derivatives with respect to normal coordinates. Only three weak peaks of the nine predicted externalβmodes were observed (88 cm^β1^, A~g~; 110 cm^β1^, B~2__g__~; and 214 cm^β1^, B~2__g__~). Crystals grown from aqueous solution were found to contain water and as much as 0.1% of BF~3~OH^β^ as a substitutional impurity. Peaks due to the OβH (OβD) stretching vibration were detected in the crystals at 3641 (2688) cm^β1^ and peaks due to the BβOH (BβOD) stretching vibration were detected as 773 (748) cm^β1^.