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

A beamsplitter, detector, source or accessory is responsive over a limited spectral
range. When these components are used together, the spectral range of the
collected data falls within the intersection of the ranges for all of the components.
That is why it is important to use components with compatible spectral ranges so
that you can obtain data over the desired range. You also need to specify a spectral
range for saving data on the Bench tab that is within the intersection of the ranges
for the components. See “Specifying the spectral range” for more information.
Checking the apodization
Turn on Apodization Correct For Sample Type in the parameter checks if you
want the software to check the appropriateness of the apodization type for the
resolution. (Use Apodization on the Advanced tab to specify the apodization. See
“Selecting the apodization type” for details.) This is a routine check that you
should normally leave turned on.
Checking the resolution
Turn on Resolution Valid For Experiment in the parameter checks if you want the
software to check the appropriateness of the resolution for the experiment. Typically
resolutions of 8 or 4 wavenumbers are used for solid and liquid samples. Gas
samples normally require a resolution of 2 wavenumbers or better (lower setting of
Resolution). This is a routine check that you should normally leave turned on.
Specify the minimum and maximum resolution for the experiment by selecting
values from the Minimum Resolution and Maximum Resolution drop-down list
boxes, respectively.
Checking
the background
for contamination
Turn on Contamination Peaks in the background checks if you want collected
background spectra to be checked for peaks due to contaminants. This is a routine
check that you should leave turned on unless you are collecting special
background spectra that contain sample peaks.
If your background material is contaminated or the accessory was not completely
cleaned after the last sample, absorptions of infrared energy by the contaminants
or previous sample materials may result in unwanted peaks in the background
spectrum. This in turn can affect the ratioing of sample spectra, producing spectral
features not due to the samples.
Note
Peaks due to atmospheric water and carbon dioxide are not considered by this
check to be contamination. ▲
Specify the sensitivity for this check by using the scroll bar. The sensitivity value
indicates how readily the check finds and reports contamination peaks. If you use
a low value, these peaks will be found only if they are large; if you use a high
value, these peaks will be found even if they are small. The current setting appears
below the scroll bar, between the minimum and maximum values.
Checking for detector icing
Turn on Detector Icing in the background checks if you want collected
background spectra to be checked for signs of detector icing. (This rarely occurs.)
Turn this check on if you are using a detector that is cooled with liquid nitrogen
(for example, an MCT or InSb detector).
Frost can form on the outside of a cooled detector dewar if the insulating vacuum
chamber surrounding the dewar has begun to leak. When this happens, the dewar
may no longer be able to cool the detector element enough to keep it responsive
and accurate across its normal spectral range.
134 Thermo Nicolet