Structure of Low-Pressure Trimethylaluminum-Oxygen Flat Diffusion Flames

Abstract

Flat diffusion flames of trimethylaluminum vapor and oxygen were studied by space-resolved photographic spectroscopy and spectrophotometry in the pressure range of 30–100 torr. Separation of the flames into two distinct zones was evident. On their oxygen side emission of aluminum lines and of molecular bands (CH, C₂ OH, AIO) was predominant, while, on the fuel side, continuum emission extending throughout the visible and near ultraviolet spectrum appeared. Photoelectric scans across the flame were obtained of the following features: nitrogen-laser radiation (3371 Å) scattered at right angles, aluminum emission and absorption (3962 Å), using a square-wave modulated hollow cathode lamp, continuum emission (4410–4530 Å) and AIO + continuum emission (4830–4890 Å). Aluminum emission was prominent on the oxygen side and decreased appreciably with increasing pressure. Aluminum absorption was measurable only on the fuel side. Continuum emission and scattering also peaked on the fuel side, the former decreasing and the latter increasing with pressure. Aluminum absorption peaks corresponded to atomic number densities of the order of 10¹² cm⁻³. AIO emission was too weak to be measured, even at the lowest pressure.