High-speed time-resolved spectrometry

There are several types of measurements for which standard rapid-scanning interferometers may be inappropriate. These include hyperspectral imaging (Section 14.5), high-speed time-resolved spectrometry (Section 19.2), photoacoustic spectroscopy (Section 20.3), and sample modulation spectroscopy (Chapter 21). For these measurements it is necessary to hold the optical path difference constant while a measurement is made, after which the OPD is rapidly advanced to the next sampling position and then held constant once again for the next measurement. This process is repeated until all the data needed to obtain the interferogram are acquired. Such interferometers are called step-scan interferometers. 

One shortcoming of gas phase ion mobility spectrometry is its inability to maintain high resolving power at small scale. The separation efficiency of time-of-flight ion mobility spectrometry is limited by the low-field requirement, the speed of ion shutter gate relative to the drift time of analyte ion, and the space charge effect. 

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