Multiple-sound-source-excitation quartz-enhanced photoacoustic spectroscopy based on a single-line spot pattern multi-pass cell

Multiple-sound-source-excitation quartz-enhanced photoacoustic spectroscopy (MSSE-QEPAS) based on a single-line spot pattern multi-pass cell (MPC) is reported for trace gas detection. The single-line spot pattern MPC is designed to make a laser beam pass through a quartz tuning fork (QTF) 60 times, thus producing 60 sound sources between the two QTF prongs. These sound sources excite the QTF operating at fundamental resonance mode in phase, resulting in a signal gain factor of ∼20. A theoretical mode based on convolution method is proposed to explain the working mechanism of MSSE-QEPAS.