Removing aperture-induced artifacts from Fourier transform infrared intensity values

Area of Science:

• Spectroscopy
• Analytical Chemistry
• Physical Chemistry

Background:

• Fourier transform infrared (FTIR) spectroscopy is susceptible to artifacts at high spectral resolution.
• Two specific artifacts, a 2f alias and aperture-induced line shape distortion, affect spectral data.
• Previous studies have alluded to these issues, but comprehensive correction methods were lacking.

Purpose of the Study:

• To identify and characterize two significant artifacts in FTIR spectroscopy.
• To develop and demonstrate effective correction methods for these anomalies.
• To quantify the impact of these artifacts on integrated-band intensities.

Main Methods:

• Utilized Fourier transform infrared spectroscopy at a spectral resolution of 0.1 cm(-1).
• Investigated light reflection off the aperture causing a 2f alias.
• Analyzed the effect of a warm aperture annulus on cooled detectors.
• Implemented novel correction procedures for both identified artifacts.

Main Results:

• Observed and quantified the 2f alias artifact from double modulation.
• Identified distorted line shapes and anomalous intensities in the fingerprint region due to aperture effects.
• Demonstrated the efficacy of the developed correction methods.
• Found pre-correction integrated-band intensities to be in error by up to 12%.

Conclusions:

• The developed corrections effectively remove 2f alias and aperture-induced artifacts in FTIR spectra.
• Accurate spectral data is crucial for reliable quantitative analysis in FTIR.
• These corrections enhance the precision of integrated-band intensity measurements in FTIR spectroscopy.