Double Lorentzian Line Shape

 


The double-Lorentzian (DL) is an excellent alternative to the Doniach-Sunjic (DS) line-shape for asymmetric peaks. The DL line-shape is very similar to a Voigt function, but with the Lorentzian width different for the two sides of the peak. It has many advantages over the DS:

  • It provides for much better fits (as shown in the example below).
  • The area of the peaks can be quantified when the DL line-shape is employed since it is
    integrable. The area of the DL peaks converges in the same way as, e.g., the Voigt functions. In contrast, the DS line-shape cannot be employed for quantitative studies since the area of the peaks increases indefinitely with the integration range.
  • A smooth transition can be made from the Voigt to the DL line-shape.
  • More details can be found in the document below.

     

    Example

     

    The figure shows the best fits obtained by employing DL and DS line-shapes for a Fe 2 p spectrum. The fit is much better in the DL case even though extra physical restrictions were employed, such as that the area of the 2 p 1/2 branch is forced to be one half of the 2 p 3/2 branch.

     


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