software to fit optical spectra - Quantum Materials Group

Figure 4-1 This is how RefFIT looks like when it starts. No internal objects are created yet.
4.3. Parameters
A parameter in RefFIT is a number, which is used as an input for model formulas to
calculate optical quantities, and can be varied (manually or automatically) in order to improve
the match of the model and experimental spectra. The examples of parameters are Lorentzian
transverse frequency, and experimental angle of incidence. Parameter values are displayed and
can be manually edited either in the “Experimental parameters” window (Figure 4-3) or
“Model” windows (Figure 4-4).
The value is not the only characteristic of a parameter. Another essential property is the
switch, which determines if a parameter is allowed to be varied in the automated fitting (active
in fit) or not. There are also maximal and minimal values (limits) that parameters may have 17 .
To access these extra characteristics a separate window is provided, which is called
“Parameter control” (Figure 4-2). It contains the full information about the parameter, which is
currently selected. To see the characteristics of another parameter, one should select it by a
mouse click or by moving the marker to it with the arrow keys. This window also contains a
trackbar, which allows you to change the parameter value in a comfortable way by dragging it
up and down. Note that all the other windows in RefFIT will be updated in real time.
17 Although the limits can be set, the fitting routine is not yet able to take them into account
Guide to RefFIT Page 52