Production of O2(1Σ +g) in the H + O2 system
Abstract
Chemiluminescence is observed in the reaction between atomic hydrogen and molecular oxygen. Bands at λ= 1265, 1430 and 1510 nm are ascribed to transitions involving HO2, while that at λ= 762 nm is due to the O2(1Σ+g→3Σ–g) transition. Evidence is adduced to show that O2(1Σ+g) is not produced by energy-pooling from O2(1Δg), and that O2(1Δg) is itself only a minor contributor to the band at λ= 1265 nm.
The bands at λ= 762 and λ= 1430 nm both show a first order dependence on [H] and on [O2]. We examine several reactions which are possible sources of O2(1Σ+g) and conclude on the basis of the kinetic evidence, that the most probable reaction sequence is H + O2+ M → HO2+ M (4), H + HO2→ H2+ O2(1Σ+g). (6c′)
Measurement of absolute concentrations of H and O2(1Σ+g) allows estimation of the efficiency of reaction (6c′) relative to the overall loss of HO2 in reaction (6) H + HO2→ products. (6) The value obtained for the efficiency is 2.8 ± 1.3 × 10–4, so that ∼10–3 of the molecular oxygen formed in the reaction is in the 1Σ+g state.
Alternative excitation mechanisms are also assessed.