Background options

This section explains how to use the different backgrounds available in the program.

  • AAnalyzer counts with two different methods for reproducing a background. The Active Background method allows the user to employ several backgrounds simultaneously on a single fit. The Static Background (traditional) method allows the user to employ only one type of background at a time. Both methods are not compatible; selecting a method will automatically disable the other. All background options are located under the “fitting parameters” tab and can be selected by simply checking the box next to your desired background.

  • Active Background

    One of the unique features of AAnalyzer is the Active Background, which allows the user to fit with one or several different backgrounds simultaneously. In order to activate the Active Background, check any of the background boxes under the “Active Background” group box, as shown in the following image. Beware that selecting too many backgrounds from the “active Background” group box may not be beneficial, as it involves too many variables and it decreases the accuracy of the fit.

  • The following example is a Au 4d spectra fitted with an Active Background combination of Shirley and Extrinsic Simplified backgrounds (aside from the baseline). The types of backgrounds available for Active Background combinations are explained later on in this section. Please note that an Active Background allows employing one or several backgrounds at a time.

  • Graphic example


  • Shirley Background

    The user has several background options to choose from in the Active Backgrounds group box. These options are described below.

  • How to identify: The main characteristic of a Shirley Background is its flat nature. However, the background becomes noticeably higher to the left of the peak. This is due to the accumulated background generated by the scattered photoelectrons coming from the core level associated to the peak.

  • The previous example is an Au 4f spectrum. The flat extremes and the “count” difference between them are well reproduced with a Shirley Background as shown in the following images.

  • Graphic example


  • Slope (Extrinsic Simplified) Background

  • How to identify: The Extrinsic Simplified Background is also a unique feature of AAnalyzer. It is similar to the Shirley background; however, instead of producing a flat elevated background to the left of the peak, the background tilts upwards or downwards with a constant slope, as shown in the following image.

  • This example of an O1s displays an initial flat background to the right and a negatively sloped background to the left of the peak. These characteristics are well reproduced with an Extrinsic Simplified background as shown in the following images.

  • Graphic example

  • Exponential Background

  • How to identify: An exponential Background is more commonly found at low electron kinetic energies. This background grows exponentially to the left.

  • The background for this example (Sr 3d acquired with is 130 eV photon energy) is well reproduced with an Exponential Background, as shown in the following images.

  • Graphic example

  • Linear and Polynomial Background

  • How to identify: Linear and Polynomial Backgrounds are used when none of the previously described type of backgrounds is able to reproduce the data. This is mostly the case for when the peak rides on top of the background of another more dominant peak. The following is an example of a small Li 1s peak on top of the background from a silicon oxide sample.

  • Graphic example


  • The only backgrounds that can reproduce this negatively-sloped background are either the Linear or Polynomial background as shown in the following images.


    The Linear background

  • Graphic example

  • Graphic example


  • The Polynomial background

  • Graphic example

  • Graphic example

  • Both the Linear and the Polynomial backrgrounds are able to reproduce this background example of a Li 1s spectrum.


    Static Background (traditional method)

  • To activate a Static Background, check the “use static” box and choose the type of background you wish to use. Checking the “use static” box will disable the “Active Background” group box. The following example is a Au 4f spectrum fitted with a Shirley Static background.

  • Graphic example

  • To manually edit the background limits, input new values for “x” in the “bkgn limits” group box and check the “apply” box.