A technique using rapid-scan Fourier transform infrared (FT-IR) spectroscopy to observe reversible dynamic changes of systems under an externally applied perturbation is introduced. The technique does not require a lock-in amplifier or synchronization between the applied perturbation and the spectral acquisition. With the use of a carefully designed sampling rate with respect to the perturbation period and reconstruction of the observed spectral intensities, dynamic spectral intensities of the system are obtained. Due to the repeated behavior, the reconstructed spectral intensities can be used to represent the dynamic characteristic of the system. The experimentation time of the rapid-scan technique is significantly shorter than that of the step-scan technique. The influences of noise and experimental parameters on the observed spectral intensities are verified. Applications of the technique to systems with sinusoidal dynamic changes and exponentially decaying dynamic changes are demonstrated.
Sanong Ekgasit, Heinz W. Siesler, and Paul A. M. Steeman, "Dynamic Infrared Spectroscopy Using the Rapid-Scan Technique," Appl. Spectrosc. 53, 1535-1541 (1999)