Calculation of the apparatus function for the case of a generalized Voigt contour

The Rayleigh-Bracewell method of finite differences is applied to cases where the apparatus function is either entirely Lorentzian or results from the superposition of Lorentzian and Gaussian components. A firstorder correction is calculated, and order of magnitude estimates are given for the remaining terms in the series expansion representing the correction. The method is employed to correct self-reversed contours of spectral lines.