software to fit optical spectra - Quantum Materials Group

Figure 3-23 Adding the four available chi-square terms.
The weights of all chi-square terms w ν are equal to one by default. However, here we
have a case, when this is not the optimal choice. The reason is (see sections 2.1.2 and 2.1.3)
that we did not set the proper data error bars. RefFIT always sets to them 0.01 unless other
values are explicitly specified. I would suggest you to set w ν equal to 1000 for the term “R”, 1
for the terms “E1” and “E2” and 1.0E-6 for the term “S1” (I found these values after several
tries and errors). The window “Fit” should look like at Figure 3-24.
Figure 3-24 The “Fit” window. Four chi-square terms are selected.
Now you can click (which is my ‘favorite’ button, by the way). It takes seconds (or
even fractions of a second) to reach a better fit that you can see at Figure 3-25. Not bad for a
model with only two oscillators! By the way, do not forget to save the model.
Guide to RefFIT Page 40