Perkin-Elmer MultiScope System, User Reference

Page: 92 / 142

92 . MultiScope System Microscope User's Reference
If You Must Collect the Sample Spectrum First
To collect the background spectrum with the same aperture as the sample
spectrum, you usually set the aperture with the sample in place, move the sample
before you collect the background spectrum, and finally return the sample and
collect its spectrum.
With some samples, it is inconvenient or even impossible to move the sample and
then replace it precisely, for example, if the sample is an electrical contact on a
circuit board. The following procedure enables you to collect the sample spectrum
first, before you move the sample and collect the background spectrum. This
example shows how to perform the procedure in reflectance mode.
1. With the sample under the microscope, set the aperture.
2. Collect a spectrum of the sample in single-beam mode.
3. Remove the sample without changing the aperture.
4. Put the reference mirror on the sample stage.
5. Still without changing the aperture, focus on the mirror.
6. Collect a single-beam spectrum of the mirror into the background region of
the FT-IR.
7. Divide the single-beam sample spectrum by the background spectrum to
obtain the ratioed spectrum, using the difference command in IRDM or
GRAMS, the spectral calculator in Spectrum, or the diff command on the
Spectrum BX or Model 1600.