Pulsed Time-Resolved Fourier Transform Infrared Emission Spectroscopy

Abstract

A variety of time-resolved Fourier transform infrared (FTIR) techniques have been described in the literature.1–11 The basic concept is to trigger a transient event such as a chemical photolysis, for example with a lamp or a laser, and to acquire absorption or emission amplitudes with the Fourier transform interferometer at specific time delays after the triggering event. One method steps the mirror to a new fixed position and takes a time-resolved trace at each position. The difficulty with this method comes in the long-term instrument stability of the mirror position in this "step and stop" mode of operation.2–4 Another method allows the mirror to sweep rapidly and continuously, and data at a number of times after a single triggering event are collected as the mirror sweeps. The point in the interferogram where the trigger occurs is varied, so that data are obtained at all mirror positions and times. These data are then used to construct interferograms at a number of different time delays after the triggering event. This method has sometimes been found to have artifacts if there is Jitter in the sweep speed of the mirror or if the amplitude of the initiating source is not constant.5