Light-Induced Thermoelastic Spectroscopy Based on VP-MQTF for Simultaneous Measurement C₂H₂ and CH₄

This article introduces a light-induced thermoelastic spectroscopy (LITES) system based on a vacuum-packaged miniature quartz tuning fork (VP-MQTF) for the simultaneous detection of acetylene (C2H2) and methane (CH4). The VP-MQTF stands out due to its compact size and high Q-factor. Its small dimensions enable an enhanced thermoelastic response, leading to stronger signals in the LITES system. In addition, the vacuum-packaged design of the miniature quartz tuning fork (MQTF) not only achieves a higher Q-factor but also mitigates the issue of frequency drift commonly observed in traditional quartz tuning forks (QTFs) after prolonged exposure to air. By employing the VP-MQTF as a detector, the LITES system successfully demonstrated the detection of C2H2 and CH4. Experimental results revealed minimum detection limits (MDLs) of 672 ppb for C2H2 and 947 ppb for CH4. Furthermore, the system exhibited excellent linearity in detecting both gases, with correlation coefficients (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R} ^{{2}}$ </tex-math></inline-formula>) of 0.99854 for C2H2 and 0.99782 for CH4.