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SECTION CONTENT
Synthetic spectra
Introduction
Fourier Transfer Spectrometer
Ozone facilities
Experiment set-up
Data reduction
Assignment of lines

Synthetic spectra

  1. The transmittance is given by

    where K(s, T, P) is the absorption coefficient depending on the wavenumber, temperature, and pressure. This coefficient may be written as

    where S(T) is the line strength and f (s - so , T, P) is the line profile. For this last one, we use the Whiting expression modified by Oliveiro and Longbothum. [Ref.: J-J. Olivero and R.L. Longbothum, J.Q.S.R.T 17, 233 (1978)]

  2. The following step is to convolute the transmittance with the apparatus function. This convolution may obviously been applied to any experimental set-up.
    For a FT spectrometer, the apparatus function is first of all due to the maximum path difference which is limited; this function could be written as

    where L is the maximum path difference. Various numerical apodization could be used as for example

  3. The next step is to convolve this function with a second one, due to the entrance diaphragm

    This leads to a shift in frequency

    proportional to the wavenumber and the square of the radius r of entrance diaphragm.

    f being the entrance focal of the apparatus.
    Then the entire apparatus function is

    where j  is a parameter which describes the asymmetry of the line.