Other Sample Modulation Measurements with Step-Scan Interferometers

OTHER SAMPLE MODULATION MEASUREMENTS WITH STEP-SCAN INTERFEROMETERS... 

Rapid reversible processes can be studied by FT-IR spectrometry in at least four ways, two using rapid-scan interferometers and two using step-scan interferometers. Three of these approaches, asynchronous sampling and stroboscopic measurements with a rapid-scan interferometer and time-resolved spectroscopy with a step-scan interferometer, were described in Sections 19.2 and 19.3. The fourth approach involves the use of a step-scan interferometer and some type of sample modulation. We have seen one application in the earlier part of this chapter, and two other applications will now be described. The reorientation of liquid crystals induced by rapid switching of the electric field to which they are being subjected has been studied by at least three of these approaches. Results have been summarized in an excellent article by Czamecki [17]. In this section we discuss the application of sample-modulation FT-IR spectrometry to this problem. 

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