software to fit optical spectra - Quantum Materials Group

4.9.2. Graph contents
To set the graph contents, one should double-click on the white (inner) area of the graph
(Figure 4-14). In the window “Graph contents” (Figure 4-16) one can select the curves to show
in the graph and specify their appearance.
Figure 4-16 The “Graph contents” window.
It is possible to plot five types of curves: “DATA”, “MODEL”, “CHI-SQ”, “MULTI”
and “FREQ”.
The curves of the “DATA” type represent experimental spectra, loaded as datasets (see
section 4.8). They can be plotted either as symbols of different shape and size, as lines, as error
bars, or as a combination of these.
The “MODEL” type corresponds to model output quantities (transmission, conductivity
etc.). Model curves are always continuous.
A curve of the “CHI-SQ” type shows the square of the difference between experimental
and model spectra (chi-square). It is used to estimate the fitting match. It is this value, which is
minimized in the fitting procedure (see section 2.1.2).
The “MULTI” type is used to show the contribution of all Lorentz oscillators, included in
the model, separately. Obviously, it applies only to the Drude-Lorentz model type and only to
the additive quantities, such as the outputs “E1”, “E2”, “S1” and “S2” of the “Dielectric
function” model.
The “FREQ” is a special curve type, which indicates the transverse frequencies of the
Lorentz oscillators in a form of dashed vertical lines.
In order to specify the curves to be plotted one should first check the corresponding
buttons in the groups “Curve type” and “Quantity”. The full list of available curves, according
to these buttons will be shown in the “Available curves” section. The next step is to select some
curves from this list (using the mouse, possibly in combination with the CTRL and SHIFT
keys) and move them to the list “Graph curves” by clicking the button. In order to remove
curves from the “Graph curves” list one should select them and click the button.
Guide to RefFIT Page 75