Diffraction in a Fourier-transform spectrometer.

The distortions of the line shape and the shifts of the line positions caused by diffraction in a Fourier-transform spectrometer are described. A simple rule of thumb to calculate the amount of the line-shape distortion is presented. Two methods for the determination of the shifts of the line positions are presented and compared. We also present an approximation for the dependence of the line-position shifts on the solid angle of the source and on the radius of the diffracting hole. Finally we present a method to study the shifts of the line positions experimentally, and some measured results are compared with theoretical ones.