A kinetic investigation of the reaction Ca + O3 over the temperature range 213–383 K

Abstract

The reaction Ca + O₃→ CaO + O₂ has been studied by the pulsed multiphoton dissociation of calcium acetyl-acetonate vapour at 193.3 nm, which produced Ca atoms in an excess of O₃ and He bath gas. The reaction was then followed either by time-resolved laser-induced fluorescence spectroscopy of atomic Ca at 422.7 nm [Ca(4 ¹P₁–4 ¹S)], or by time-resolved molecular chemiluminescence at λ > 695 nm [CaO(A ¹Σ⁺–X¹Σ⁺), Δv < 4]. The rate coefficient is given by k(212 < T/K < 384)=(8.23 ± 1.08)× 10^–10 exp[–(1600 ± 300) J mol^–1/RT] cm³ molecule^–1 s^–1, where the quoted uncertainties are 2σ. This result is then compared to the predictions of long-range capture theory. Finally, there is a discussion of the impact of this reaction on the chemistry of meteorablated calcium in the upper atmosphere.