Modeling Frequency Response of Photoacoustic Cells using FEM for Determination of N-heptane Contamination in Air: Experimental Validation

We briefly present the basic principle of the photoacoustic effect in gases. We present the equations and boundary conditions governing the acoustic field generated by the absorption of a modulated laser beam. We solve these equations using Finite Element Methods and compare the results with experiment. We find that apparently there are effects not taken into account in the classic acoustic theory as we find a larger damping than theory predicts. However, we see that these effects have significant negative influence on the quality factor of the cell and thereby the performance limit.