Quenching of singlet molecular oxygen, O2(a 1Δg) and O2(b 1Σ +g), by H2, D2, HCl and HBr

Abstract

Using a discharge flow/shock tube measurements have been made of the quenching of O₂(a ¹Δ_g) and O₂(b ¹Σ⁺_g) by H₂ and D₂ at 292 K and between 500 and 1000 K. Results are also reported for the quenching of O₂(b ¹Σ⁺_g) by HCl over a similar temperature range and by HBr at 292 K. No measurements were possible for HBr at high temperatures. The two excited states differ in the temperature dependence of their quenching rate constants: the results for O₂(a ¹Δ_g) can be fitted approximately to the Arrhenius equation, while those for O₂(b ¹Σ⁺_g) change only slightly with temperature. The results are considered in terms of current models for electronic energy transfer.