THE EFFECT OF APODIZATION AND FINITE RESOLUTION ON FOURIER-TRANSFORM RAMAN-SPECTRA

The effects that finite resolution and choice of apodization function have on Fourier transform (FT) Raman spectra are illustrated by the 839 cm-1 (nu-1) and 914 cm-1 bands of KMnO4. FT-Raman spectra were recorded at 0.5, 1, 2, 4, 8, 16 and 32 cm-1 resolution using boxcar, Norton-Beer (strong, medium and weak) and triangular apodization functions at each resolution. The results show the dramatic changes in bandshape that occur as the ratio (resolution/true full width at half height of band) increases. The changes were measured in terms of the full width at half height of the band, the height of the band, the area of the band and the bandshape (expressed as a sum of Lorentzian and Gaussian lines). At a given resolution the degree to which each of these characteristics is affected is strongly dependent on the choice of the apodization function.