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The Pearson VII is also another broad approximation to the Voigt line shapes. The fitted parameters from the Pearson VII line shape though contain no information on the underlying physical properties that originally caused the broadening effect. This means that although this line shape can be used to model the peaks, the parameters that result are not correlated to any real broadening process. At intermediate values, however, this line shape approximates a Voigt extremely well. As the Pearson width (M) approaches 1, it resembles a Lorentzian in character and as it approaches infinity, it becomes Gaussian. The intensity under the peak wings increases dramatically as (M) becomes much less than 1 which does not correspond to any known broadening process.
where M = Pearson "M" width
NOTE: For all of the more complex line shapes including the Voigt, Mixture, and Pearson VII, the peak shape can be easily changed from one extreme to the other (either all Gaussian or all Lorentzian ) during the fit. Use caution when fitting the data as it is very easy to fit too many or too few peaks to a curve when the line shape can be manipulated to fit a variety of line widths. | 
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