Atomic resonance fluorescence spectrometry for the rate constants of rapid bimolecular reactions. Part 2.—Reactions Cl + BrCl, Cl + Br2, Cl + ICl, Br + IBr, Br + ICl
Abstract
Atomic resonance fluorescence spectrometry has been used to measure directly the rates of rapid bimolecular reactions of halogen atoms (2P) with halogen molecules at 298 K. Low concentrations of atoms (∼1011 atom cm–3) were generated in a flow system with a discharge-bypass. The following rate constants (cm3 molecule–1 s–1) are reported: Cl + BrCl → Cl2+ Br, k1=(1.45 ± 0.20)× 10–11; Cl + Br2→ BrCl + Br, k2=(1.20 ± 0.15)× 10–10; Cl + ICl → Cl2+ I, k3=(8.0 ± 1.0)× 10–12; Br + ICl → BrCl + I, k4=(3.0 ± 0.8)× 10–14; Br + IBr → Br2+ I, k5=(3.5 ± 0.6)× 10–11. k2 is equal to ∼0.5 of the hard sphere bimolecular collision frequency at 298 K.
The values for k2 and k4 ae in good agreement with integral reaction cross sections determined in crossed molecular beams.