Depth Profiles in Coated Paper: Experimental and Simulated FT-IR Photoacoustic Difference Magnitude Spectra

Abstract

Experimental photoacoustic (PA) magnitude spectra of a coated paper and the uncoated basepaper are presented. The normalized and scaled PA magnitude spectra are used to calculate difference magnitude spectra. It was decided to scale all PA magnitude spectra to (low) equal intensity at the approximately optically thin spectral range before subtraction. Then no infrared (IR) bands of identical band shape and height (as needed for common difference spectroscopy) in either PA magnitude spectrum are needed. Contributions of the two individual layers to the IR-PA magnitude spectrum of the coated paper are separated in the difference spectrum by their sign. An increasing relative contribution of the coating layer with an increasing phase modulation frequency is found. On decreasing the thermal length to a value near the coating thickness, the difference spectra increasingly show positive coating bands and negative bulk signals. The extension of the Rosencwaig–Gersho theory to a double-layered system introduced by N. C. Fernelius [J. Opt. Soc. Am. 70, 480 (1980) and J. Appl. Phys. 50, 650 (1980)] applied to synthetic spectra confirms the experimental observation. It is found that photoacoustic difference spectroscopy may provide quantitative depth-resolved spectral information due to the presented scaling procedure, and photoacoustic difference magnitude spectra of any polymeric laminate may therefore be calculated.

Evaluation of soil fertility using infrared spectroscopy: a review

“…The detected signal in photoacoustic spectroscopy is proportional to the sample concentration, and can be used with highly absorbing samples without any pretreatment. Using multivariate statistic analysis, such as PLS, FTIR-PAS made it a wide application with quantitative purpose in solid substance (Wahls et al 2000;Bjarnestad and Dahlman 2002;Irudayaraj et al 2002;Armenta et al 2006). …”

Identification of agricultural Mediterranean soils using mid-infrared photoacoustic spectroscopy

“…1). FTIR-PAS has been applied to depth profiling of coatings (Wahls et al, 2000), analysis of the chemical composition of materials as diverse as wood (Bjarnestad and Dahlman, 2002) and pesticides (Armenta et al, 2006), and detection of microorganisms in food products (Irudayaraj et al, 2002). A major advantage of photoacoustic spectroscopy is that it is suitable for highly absorbing solid samples without any special pre-treatment.…”

Statistical Design of Experiments: Study of Cross-Linking Process through the Phase-Resolved Photoacoustic Method as a Multivariable Response

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