A Shock-Tube with High-Repetition-Rate Time-of-Flight Mass Spectrometry for the Study of Complex Reaction Systems

The process of soot particle formation has been extensively studied. The thermal decomposition of acetylene as major decomposition product of some soot-producing hydrocarbons in different temperature ranges has been previously studied by several authors [1–3]. Shock tubes with different modern diagnostics are versatile tools that are widely used for gas-phase reaction kinetics studies [4–7]. In shock tubes, high-temperature reactions can be investigated on short time scales. The high temperature and pressure conditions behind the reflected shock wave are stable up to a fewmilliseconds. Considering these conditions, fast detectionmethods are required, that provide time-resolved information about the change of composition of the investigated mixture. A high-repetition-rate (HRR) time-of-flight mass spectrometer (TOF-MS) can simultaneously measure the concentration-time profiles for numerous species with approximately one measurement every 10 μs. Combinations of shock tubeswith TOF-MSare established for the study of complex reaction systems. The most extensive set of TOF-MS shock-tube measurements was published by Kern et al. [2, 8–10]. There are some difficulties in coupling a shock tube with a TOF-MS. The most important problems are extracting the sample from the shock tube in a reproducible way and also acquiring the resulting large amounts of data in a very short time. In the present study we used a shock tube coupled to a HRRTOF-MS to investigate the thermal decomposition of acetylene as a test system to validate the new setup. After validation, this setup has been used to investigate the thermal decomposition of (CH3)6Si2O (HMDSO).