Sample position dependence effect in photoacoustic (PA) spectrometry has been reported by several scientists. This effect must be taken into account in a PA application that requires a quantitative theoretical treatment. In this work, we experimentally investigated PA signal magnitude varying with sample-to-window distance in an MTEC Model 300 Photoacoustic Detector, which has a fixed empty (gas) volume in addition to the sample-to-window-distance-dependent gas volume. An operative method was introduced to obtain the coefficient, which considered the sample-to-window distance and the additional gas volume. With this coefficient, the one-dimensional PA model, developed by Aamodt, Murphy, and Parker, can be employed to quantitatively process PA experimental data, no matter what the sample-to-window distance is. Quantitative measurements of thermal effusivities of two samples were performed to prove this effective normalization method.
Jun Shen, Jianqin Zhou, Cheng Hu, and Jianhua Zhao, "Effective Normalization Method for Sample-Position-Dependence Effect in Photoacoustic Spectrometry," Appl. Spectrosc. 57, 186-189 (2003)