Under the active-background method the shape and intensity of the background is defined during peak-fitting. In contrast, under the traditional or static method, the background is assessed prior to peak fitting. This is illustrated in the following figure, which shows different fits of a Ti 2 p spectrum. By comparing Figures (a) and (b), it is possible to appreciate the evolution or the background shape as the fitting optimization process progresses under the active method. In contrast, under the static method, the background remains the same between iterations.
The active method has many important advantages (and no disadvantages) over the static method. Those are described in the text below. For spoilers, the area calculated with the static method for the example of the figure below underestimates the area by 6% (compare (d) with (b)). The active method always provides better fits.
The active method is implemented in AAnalyzer® and is actually easier to employ than the static or traditional method (also implemented in AAnalyzer® for the sake of completeness).