SIGNAL ANALYSIS OF TRANSIENTS IN PULSED PHOTOACOUSTIC-SPECTROSCOPY

A finite difference model was constructed to describe the origin of the complex transients in pulsed photoacoustic spectroscopy signals. With inclusion of boundary conditions and material interfaces, the model is shown to give qualitative agreement with experimental transients. The model provides insight into the results of varying the photoacoustic-cell materials and/or geometric configuration for cell optimization. The transients are found to contain significant information regarding resonant modes in the photoacoustic cell assembly. The transient signal behavior is explained in terms of these resonant cavity modes, and it is determined which cell cavities are relevant to a given time segment of the signal. Analytical detection limits are correlated with each point on the transient signal.