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

Note
If you are studying samples that produce very small spectral peaks or have weak
spectral features, or if you are looking for small changes, make sure the signal-tonoise
ratio is high enough to let you distinguish spectral features from the noise
inherent in all experimental data. This prevents the signals containing spectral
information from being lost among the signals generated by the random movement
of electrons, building vibrations, light source fluctuations and other sources. ▲
Specifying the resolution
The Resolution parameter sets the spectral resolution of the data you collect. It
determines how close two peaks can be and still be identified as separate peaks.
The smaller the resolution value, the higher (better) is the resolution. Increase the
resolution (use a smaller value) when you need to distinguish narrower bands.
Smaller values can produce narrower bands because the points in the spectrum are
closer together.
The resolution value, along with the number of scans and mirror velocity, affects
the total collection time. For any given number of scans, increasing the resolution
(using a smaller value) increases the total collection time.
Set the resolution only as high as needed to differentiate peaks of interest and give
good search results. Setting the resolution higher will not provide more information
and can result in increased noise. Also, the higher the resolution, the longer it takes
to collect the data and the more disk space that is required to save the data.
Typically resolutions of 8 or 4 wavenumbers are used for solid and liquid samples.
Gas samples normally require a resolution of 2 wavenumbers or preferably 1.0 or
0.5 wavenumber.
To optimize resolution, start by scanning the sample at a low resolution setting;
4 wavenumbers, for example. Then increase the resolution and scan the sample
again. Overlay the spectra so you can compare their quality. Repeat this procedure
until the spectra show little or no corresponding increase in spectral information.
The lower of the last two resolutions is the preferred setting.
When the resolution is 2 wavenumbers or better (lower setting of Resolution), use
the appropriate aperture setting. A small aperture restricts the infrared beam and thus
limits the distortion that can occur at high resolutions when a large aperture is used.
Collect your sample and background spectra using the same resolution.
Selecting the final format
Final Format determines the units used for the collected data. The following table
shows the available format settings and the units used.
116 Thermo Nicolet