Retrieval of an absorption line contour from measurements of its derivative with the PA-spectrometer with a two-frequency laser

In many spectroscopy tasks, the spectral width of the radiation source and in the intensity distribution deform real spectra that creates the additional difficulties when line contour parameters are reconstructed. In this paper we propose to solve a problem of the retrieval of parameters of a spectral line contour in two stages: at the first stage to fit the measured signals and to eliminate the influence of the radiation source parameters as an instrumental function, and at the second stage to search the spectral line contour parameters only. We apply two different methods for elimination of influence of the instrumental function. Both methods are proposed as a first stage for retrieval of a spectral line parameters from measurements of the line contour derivative using the PA (photo-acoustic) spectrometer with a two-frequency laser. The first method is based on transition from an integrated equation of convolution of the instrumental function with the required function to the matrix representation. The second method is based on a possibility to separate the two above mentioned functions in a Fourier plane.