Step-Scan FT-IR Photoacoustic Spectroscopy: The Signal Phase

Abstract

The model of Rosencwaig and Gersho for the photoacoustic effect is tested. The use of carbon black samples as a phase reference to estimate the apparatus phase φ_app from the experimental signal phase φ_exp turned out to be ambiguous. A new method is presented to correct the experimental signal phases φ_exp of polymer films for the apparatus phase φ_app. The photoacoustic signal phase of some well-defined poly(ethyleneterephthalate) (PET) films is obtained. As a phase reference, transparent thermally thick polymer films were found to be more convenient and dependable than carbon black samples. The resulting phase spectra of thermally thick and thermally thin PET films confirm the Rosencwaig–Gersho theory.

Keywords

Step-scan FT-IR Photoacoustics PAS-phase Phase-resolved depth profiling

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