Quantitative analysis of a closed photoacoustic cell that uses a high compliance piezoelectric transducer

A treatment of the operation of low-frequency closed photoacoustic cells is presented, which considers the compliance of various cell elements. The optimum detector, according to our predictions, has a sensor whose compliance is large compared to that of the fluid enclosed by the cell. A simple photoacoustic cell has been built, incorporating a thin-walled piezoelectric cylinder. It was used to test the theory, and demonstrate photoacoustic detection of an absorber in aqueous solution, excited by a low-power 678 nm laser diode modulated at 110 Hz. We have detected absorbances as low as approximately 3×10-3 cm-1 (signal-to-noise ratio=1), corresponding to the absorption of light with a modulated power of 50 µW rms