Absorption Spectra of Gaseous Halide Ions and Halogen Electron Affinities : Chlorine, Bromine, and Iodine

Abstract

Absorption spectra have been taken of partially dissociated vapors of chloride, bromide, and iodide salts of rubidium and cesium. The salts have been heated by shock waves. Continuous absorption spectra characterized by sharp thresholds are attributed to the ions Cl—, Br—, and I—. The low-energy thresholds for the three ions fall at approximately 3424, 3685, and 4040 Å, respectively. From the threshold wavelengths and appropriate small environmental corrections, the electron affinities of chlorine, bromine, and iodine are determined to be 3.628±0.005, 3.378±0.005, and 3.078±0.005 eV, respectively.