A Novel Wide Temperature Range Photoacoustic Cell for Molecules in the Vapour Phase

Summary

A photoacoustic cell operating on the principle of a heat pipe has been designed and tested. The new cell is of a simple, compact design and its operational temperature range restricted by the choice of material from which the heater zone of the cell is constructed. The cell windows and microphone are kept at room temperature; morevover condensation of vapour on these components is prevented due to the presence of a sharp interface between the buffer gas and vapour. The cell can be used at the second longitudinal resonance (the pipe is closed at both ends). The usability of the photoacoustic heat pipe (PAHP) is demonstrated by observing an absorption spectrum of geraniol, C₁₀H₁₈O, in the 9 µm and 10 µm band of the CO₂-laser. This photoacoustic vapour spectrum is compared qualitatively to that of a vapour phase spectrum obtained by FTIR.