PHASE CORRECTION OF EMISSION-LINE FOURIER-TRANSFORM SPECTRA

The process of phase correction for emission line spectra with high si gnal-to-noise ratios has remained a surprisingly complicated problem t hat can seriously affect the precision of data derived from Fourier tr ansform emission spectra. Traditional methods, using a low resolution phase spectrum can produce spectra that show systematic errors in line positions and profiles. An improved phase correction strategy has bee n developed for and tested with infrared, visible, and ultraviolet emi ssion line sources. A carefully apodized transform of relatively high resolution provides the phase data. A discriminator is used to restric t the data to those points that have a sufficiently high signal-to-noi se ratio to provide a reliable phase estimate, and a smooth phase func tion is obtained by fitting a polynomial to these points. Some charact eristics of real interferograms that complicate this simple picture ar e discussed.