Fitting High-Resolution Spectra: CasaXPS Basics

1. Click on the Quantification Parameters button and go to the Regions panel.
2. Click on Create. This will make a peak region. Drag the endpoints to the desired location. To change the type of background type S for a Shirley background in the BG Type box, type L for a linear background, or T for a Tougaard background. For other available backgrounds see the CasaXPS manual. The starting and endpoints of the region can also have an offset applied to them by changing the St. Offset and End Offset values.
3. Under the Components panel click on Create to create a peak. You can drag and move the peak using the mouse if desired or you can position and change the parameters of the peak by adjusting the Area, fwhm and Position values.
4. Add more peaks as needed using the Create button.
5. You can add peak constraints by entering values into the Area Constr., fwhm Constr. or Pos. Constr. boxes. These can either be a range of values (fwhm Constr.example:1, 2.5; Pos. Constr. example: 285.00, 285.45) or a simple mathematical formula (fwhm Constr. example: A*1 (peak will be the same width as peak A); Pos. Constr. example: A+1.5 (peak will be 1.5 eV above peak A); Area Constr. example A*0.5 (peak will be half the area of peak A – useful for constraining spin orbit doublets).
6. The label for each peak can be changed in the Name box.
7. Click on Fit Components to have the program fit the peaks.
8. If desired, the residual fit can be viewed using the Residual On <-> Off button.
9. In the Annotation, Components panel, click on Apply. This will bring up the fitting components on the spectrum.