Infrared Photoacoustic Spectroscopy of Solids and Surface Species

Abstract

Infrared photoacoustic spectra were recorded over the 3900 to 1400 cm⁻¹ range with a single-beam, computer-controlled spectrometer fitted with a broad-band source and LiF and CaF₂ prisms. The exploratory results indicate that structured IR spectra of organic solids can be obtained. Various surface treatments were used to alter the chemical composition of the surfaces of samples composed of thick catalyst pellets and of thick beds of powdered silica and alumina, under controlled conditions in a reactor attached to the acoustic cell. The IR bands of resulting surface species were observable at sub-monolayer coverages. With some improvements, IR-photoacoustic spectroscopy will be a useful ancillary technique especially suited for studying surface species on thick adsorbents, catalysts, and corrosion layers.