A compact apparatus for gas-phase low-temperature kinetics study based on de Laval nozzle

We have developed a compact apparatus to investigate low-temperature gas-phase reaction kinetics. This apparatus integrates pulsed Laval nozzles with vacuum ultraviolet photoionization reflectron time-of-flight mass spectrometry (VUV-ReTOFMS) for sensitive detection of neutral-neutral reaction products. A uniform supersonic flow (M = 3.56) was established in a N₂ nozzle, with measured temperature and density of (85.1 ± 4.7) K and (4.49 ± 0.60) × 10¹⁶ molecule cm^-3, respectively. The reaction between methylidyne radical (CH·) and propene (C₃H₆) was investigated using 118 nm VUV-ReTOFMS. A dominant C₄H₆ + H product channel was observed, consistent with previous studies, demonstrating the product detection capability of the apparatus. This compact and sensitive instrument will be coupled with the Dalian Coherent Light Source (DCLS) to enable isomer-resolved product detection in low-temperature reactions.