The Nature of Apodization in Fourier Transform Spectroscopy

Since the introduction of commercially available rapid scan Fourier transform IR (FT-IR) interferometers there has been a dramatic increase in both the number of laboratories which utilize FT-IR instruments on a routine basis and the number of scientific applications in which FT-IR interferometry offers advantages over conventional dispersion spectroscopy. As a result many who have come to use Fourier transform interferometers in their studies because of its throughput (Jacquinot) and multiplex (Fellgett) advantages are less familiar with the more subtle points which must be considered when a Fourier transformation of digitized information is performed. To this end a study of the effects of apodization on bandshape and resolution is presented with particular attention on intensity considerations in the computed spectrum. In particular, problems related to (1) the detection of weak bands in the vicinity of strong ones and (2) false intensities due to artificial overlap of two bands which are in near proximity are addressed.