Recombination of ground-state halogen atoms. Part 1.—Radiative recombination of chlorine atoms

Abstract

Both ¹Σ⁺_g ground state and ³Π_ou⁺ excited state Cl₂ molecules were formed during recombination of ground state Cl ²P atoms in a discharge flow system using total pressures near 1 torr of Ar or Cl₂ as a third body, and in the temperature range 298 < T < 430°K. Under these conditions, the intensity of red and near infra-red emission from the excited state (³Π_ou⁺–¹Σ⁺_g) was not simply proportional to [Cl]², as had been supposed, but had a more complex dependence on [Cl] and third-body concentration [M]. The rate-determining steps involving Cl₂(³Π⁺_ou) include vibrational quenching although not electronic quenching by M, and a rapid exchange reaction (4): Cl(² P)+ Cl(² P)+ M→Cl₂(³Π_ou⁺)+ M (1), Cl₂(³Π_ou⁺)→Cl₂(¹Σ⁺_g)+hv(λ > 5000 Å)(2), Cl(² P)+ Cl₂(³Π_ou⁺)→Cl₂(non-radiative)+ Cl(² P). (4)