Shock wave studies by mass spectrometry. III. Description of apparatus; data on the oxidation of acetylene and of methane

Abstract

Apparatus has been constructed which makes it possible to study a wide variety of very fast reactions in the gas phase. In this apparatus, gas is sampled from a reflected shock wave, directly into the ion source of a time-of-flight mass spectrometer. Changes in concentration during reaction of a gas mixture are followed by recording the mass spectra which are produced at intervals as short as 20 u s. A method is described of recording a number of consecutive mass spectra from several oscilloscopes arranged in series. A study has been made in this apparatus of the high-temperature oxidation of acetylene. It is shown that water and carbon monoxide are produced simultaneously during the reaction, suggesting that both of these combustion products are formed directly in the main chainbranching cycle. A reaction mechanism is proposed in which the important step leading to regeneration of hydrogen atoms is C 2 H+0 2 -> 2CO+H. Some results of a preliminary study of the oxidation of methane at 1850 to 2050 °K are also reported. It is observed that under our conditions significant amounts of C 2 hydro carbons are formed early in the main chain-branching oxidation reaction.