INFRARED PHOTOACOUSTIC-SPECTROSCOPY OF SOLIDS AND LIQUIDS

We discuss the application of photoacoustic methods to vibrational spectroscopy on liquid and solid specimens. Based on tunable CO2 lasers as radiation sources, examples are given to demonstrate the high sensitivity (sub-monolayer) and spectral resolution that can be achieved in the mid-infrared. Spectra of aqueous solutions, powders and single crystals of ammonium sulphate are presented. Photoacoustic reflection-absorption spectroscopy (PARAS) has been developed to record spectra from thin films on conductors, and spectra are shown of aluminium oxide films on aluminium. A technique employing an open membrane spectrophone allows spectra to be recorded from samples outside the acoustic chamber. © 1979.