Emission and Two-Body Recombination in Bromine

Abstract

The visible emission from hot, partially dissociated bromine raised to temperatures as high as 2500°K by means of a shock wave has been studied as a function of wavelength and temperature. At total pressures around 1 to 2 atmos in a 1‐in. shock tube, the emission is continuous. It is caused by two‐body atom recombinations of two types, one involving two unexcited Br atoms and the other involving one excited atom and one unexcited atom. The first type yields excited Br₂ molecules in the states ³π_1u and ¹π_u, while the latter type produces excited molecules in the ³π₀+_u state. Proof of these mechanisms comes through analysis of emission spectra in terms of the potential diagram of bromine and through photomultiplier observations of the emission intensity at specific wavelengths as it varies with temperature and Br atom concentration. Some information is obtained on the shapes of the excited state potentials in the high energy region and an assignment of the transitions responsible for visible absorption in bromine is recommended.