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

Setting
Boxcar
N-B* Weak
N-B* Medium
N-B* Strong
Description
The interferogram is unweighted; that is, the data are simply
truncated at the beginning and end. Use this type when you
are measuring a gas sample, want maximum resolution and
are not concerned about ringing effects (side lobes). The
greatest amount of ringing will be present with this type.
This setting has a less pronounced smoothing effect on data
than do the N-B medium and N-B strong types and degrades
the resolution more than those types. This setting is
generally not recommended and is normally used only to
reproduce the results of other experiments that used it.
Has a smoothing effect on data which is between that of
N-B weak and N-B strong. It suppresses side lobes as much
as possible given that it only moderately degrades the
resolution. The side lobe suppression is more significant
than for N-B weak apodization. This setting is suitable for
most normal samples; it gives results virtually identical to
those obtained with Happ-Genzel.
This setting has a greater smoothing effect on data than do
the N-B weak and N-B medium types and does not degrade
the resolution of the spectrum. The side-lobe suppression is
more significant than for N-B medium apodization. Side
lobes appear on both sides of peaks and are more
pronounced for sharper peaks. Use this setting only when
the best possible resolution is required.
* “N-B” stands for Norton-Beer.
Specifying the
sample spacing
Note
Sample Spacing determines the number of zero crossings of the reference laser and
the allowed spectral range.
Sample Spacing is normally set to 2 (for mid-IR). If you want the spectral range to
extend beyond 7899 wavenumbers, set Sample Spacing to 1 (for near-IR). If you
want to reduce the processing time for a series experiment, set Sample Spacing to 4.
If you use a setting of 4, be sure to use an optical filter to filter out frequencies
above 3950 wavenumbers. This prevents higher frequency peaks from being
“folded over” into the actual collected range. ▲
The Sample Spacing setting affects the total number of data points collected over a
given spectral range. For example, a setting of 1 doubles the number of data points
as compared with a setting of 2. Similarly, a setting of 4 results in half as many
data points as a setting of 2.
If you want the sample spacing to be set automatically based on the spectral range,
turn on Set Sample Spacing Based On Spectral Range. The Sample Spacing dropdown
list box is unavailable when the check box is on.
138 Thermo Nicolet