| 摘要 |
A laser photoacoustic spectroscopy (PAS) apparatus for detecting gaseous analytes comprises a plurality of tuneable lasers, such as wavelength tuneable diode lasers (TDLs) and a photoacoustic cell 12, where each of the lasers is tuned to excite one or more of the analytes of interest. The apparatus may include a Michelson interferometer 16 that is used to measure an acoustic signal produced by a cantilever microphone 14 located in the photoacoustic cell and the cell may comprise a sample chamber and a balancing chamber. The outputs from the lasers may be coupled into a single beam used to excite the analytes simultaneously or sequentially using signal multiplexing techniques. Accurate monitoring of gas species at low concentrations may be achieved, such as is suitable for assessing ageing of materials based on the physical and chemical processes indicated by the gases evolved or consumed by the materials.
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