The Detection of Atoms and Free Radicals in Flames by Mass Spectrometric Techniques

Abstract

A mass spectrometric method employing a molecular beam gas sampling system has been developed for the detection of atoms and radicals in chemical reactions. Background signals have been virtually eliminated by mechanically modulating the molecular beam and applying phase detection to the ion signal. The application of the method is illustrated by examples of low‐pressure flames. In the hydrogen‐oxygen flame H, O, and OH have been positively identified. The mass spectrum of a simple hydrocarbon flame, such as the methane‐oxygen flame, is complicated by the presence of a large number of stable components generated in the flame. In the methane‐oxygen flame the stable intermediates include C₂H₂, CO, CH₂O or C₂H₆, CH₄O, and C₄H₂. The methyl radical has been clearly identified in the methane‐oxygen flame. A search for the HO₂ radical in the hydrogen‐oxygen flame was made without obtaining positive results. The HO₂ detection problem is discussed in detail.