Fitting with doublet peaks

  • Fitting a doublet peak is a very similar process to that of a singlet. Once the data of your doublet peak is plotted, you may draw the peak by selecting the “edit peaks with mouse” box located on the right side of the window, and dragging the mouse across the width of the desired peak (Note that you only have to input one peak when Fitting doublets). Your window should look like the following images.

  • If you are having trouble drawing a peak, please refer to the “open files” and/or “Fitting singlet peaks” instructions.

  • Once you have inputted your peak, AAnalyzer will create parameters for your new peak in the “fitting parameters” tab. Each row represents the parameters for a peak. Under this tab, make sure to specify that your peak is a doublet. Also make sure to add a background (refer to “Fitting Singlet Peaks” instructions for more information about baselines and backgrounds).

  • The final steps before beginning the fitting process are to specify the splitting and the ratio of your peak. If you already know the branching ratio of the doublet (0.5 for p-type, 0.666 for d-type, and 0.75 for f-type), indicate it on the “ratio” cell located near the upper left corner of the window. Make sure that you set the ratio as “fix”. This will ensure an optimum fit of your peak without modifying the “ratio” value.

  • Then, input the value of the splitting in the splitting box located under the “Fitting Parameters” tab. If you need assistance to determine an approximate value of the splitting, uncheck the “edit peaks with mouse” box under the “data and fits plot” tab, and click-and-drag your mouse from the crest of one branch to the other. This will give you an approximate difference between the two centers of energy. This difference will be shown as a “width” value in the upper right corner of the “data and fits plot” tab.

  • Make sure that you select the “splitting” as a “free” parameter; this will allow AAnalyzer to find an optimum value of the splitting.

  • To begin the fitting process, press any of the first two fitting buttons located on the upper right corner of the window under the “data and fits plot” tab. Both branches are fitted with the same lorentzian and gaussian values. Fit 1/1 – The first fitting option fits all “free” parameters (parameters in red font) simultaneously. This method provides a fast and efficient fit. Fit 1/1 ? – The second fitting option fits all parameters simultaneously as with the first button. Then, it fixes all free parameters except one and optimizes it individually. This process is repeated for as many “free” parameters you have (each time optimizing a different single parameter). This method provides a more precise optimized value for each parameter. For information about the function of the 3rd and 4th buttons please refer to the “simultaneous fitting” section.

  • The fitting process is still incomplete at this point. AAnalyzer automatically fits all peaks using a “fixed” Lorenztian value of 0.085 eV, which corresponds to the natural Lorentzian width of Si 2p. However, the previous example displays a doublet of Au 4f, whose natural Lorentzian width is approximately 0.42 eV. Inputting known “fixed” values to your peak’s parameters will increase the accuracy of the fit. If you know the Lorentzian width of your core level, input the new Lorentzian value in the corresponding peak under the “fitting parameters” tab. Another option would be to set the value as “free”; this will allow AAnalyzer to find an optimum value.

  • Make sure to press one of the first two fitting buttons to perform a fit and visualize the changes made in the “fitting parameters” tab. The result is a more precise fit.

  • To save your progress, click the “save” button in the upper right corner of the “data” tab. This will save all information inputted in the “data” tab, as well as parameter information in the “fitting parameters” tab. For more information about other saving options, please refer to the “Saving Options” instructional tab. When you reopen AAnalyzer, you will be able to access any project you worked on by selecting it in the pop up window mentioned at the beginning of this section. The last project you saved will be the default file in the open box.