Thermonicolet Omnic Software User's Guide 6.1 (PDF) - Charles E ...

2. Choose Subtract from the Process menu.
Subtract is available
in the Process menu only
when two spectra are selected.
The Subtract window appears with the sample spectrum displayed in the top
pane and the reference spectrum below it.
Note
If the spectra do not have the same resolution, the spectrum with the higher
resolution will be temporarily deresolved to match the resolution of the other
spectrum. The subtraction operation will take longer in this case. ▲
The spectral region displayed in the Subtract window is the same region that
was displayed when you chose Subtract. To display a different region of all
the spectra, use the view finder.
The difference spectrum is displayed full scale in the bottom pane. This
spectrum is the result of subtracting the reference spectrum from the sample
spectrum using the subtraction factor shown to the left of the result.
To expand or contract the Y-axis of the difference spectrum, click the buttons
to the right of the bottom pane. Expanding the spectrum helps you see small
features.
Each time you click the Expand button, the scale of the Y-axis doubles.
Each time you click the Contract button, the scale of the Y-axis is reduced by
one-half.
If you want to reverse the order of subtraction, click the double-arrow to the
right of the spectra. The order of the spectra is reversed and the new
difference spectrum is displayed in the bottom pane.
214 Thermo Nicolet