Ultra-rapid-scanning Fourier transform infrared spectrometry

Several applications of Fourier transform infrared (FT-IR) spectrometry are discussed where both conventional rapid-scanning interferometers and step- scan interferometers are unable to provide the needed information. A new in terferometer is described by which it is possible to acquire interferograms with 0.25 cm optical path difference (4 cm(-1) spectral resolution) in les s than 1 ms. The moving element of this interferometer is a tilted mirror t hat continuously rotates at a speed of up to 500 Hz. The performance of thi s spectrometer is demonstrated by examining the spark-initiated combustion of ethane and methane in air. The formation of vibrationally excited CO2 an d H2O, with lifetimes approaching 50 ms, was observed. (C) 1999 Elsevier Sc ience B.V. All rights reserved.