A kinetic investigation of the reaction Ca + O 3 over the temperature range 213–383 K

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.