|Sensitivity Issues in Step-Scan FT-IR Spectrometry
A typical step-scan measurement might utilize a step
rate of 1 laser fringe per second producing modulation frequencies 5000 times lower than
the typical rapid-scan measurement. Thus, the infrared modulation frequencies would be in
the range of 0.25 to 0.025 Hz. The frequency spacing between adjacent spectral elements is
then only 0.24 milliHertz. It is the very low modulation frequencies and their close
spacing that make step-scan measurements susceptible to low-frequency noise.