Quartz tuning fork enhanced photothermal spectroscopy gas detection system with a novel QTF-self-difference technique

摘要

A novel self-difference technique based on quartz tuning fork (QTF) is proposed in this manuscript. C2H2 is selected as the target analyte to verify the effectiveness of this technique. The measurement technique consists of two laser beams, one laser beam passes through the gas cell as the probe laser beam and the other beam is used as the reference laser beam. The vibration direction of the QTF caused by the two laser beams is opposite by adjusting the position where the two laser beams illuminate QTF. The two quartz tuning fork enhanced photothermal spectroscopy (QEPTS) signals are subtracted by utilizing the mechanical vibration characteristics of the QTF. As a result, the SNR increases 5.1 times in QTF-self-difference based system compared to a traditional differential gas detection system. Finally, the system achieved a minimum detection limit (MDL) of 723 ppbv, corresponding to a normalized noise equivalent absorption coefficient (NNEA) of 7.85 x 10(-10) cm(-1) W/Hz (1/2). (C) 2019 Elsevier B.V. All rights reserved.