Studies of ground-state 2 P ? halogen atoms using atomic resonance absorption

Known concentrations of ground-state Br, Cl and I 2P atoms can be formed by the rapid stoichiometric reactions: [graphic omitted] k1, defined by –½[Br2]–1d ln[O]/dt, is reported as (8.7 ± 3.0)× 10–12 cm3 molecule–1 s–1 at 298 K. These reactions provide simple absolute calibrations for resonance line absorption intensities with Br, Cl and I 2P atoms in discharge-flow systems. Photolysis of Br2 and of ICl by H λ 121.6 nm radiation present in the atom resonance lamps leads to the formation of excited Br and I atoms. The effects of these phenomena on measurements of atom concentrations by resonance absorption are considered.