Experimental and modelling study of the recombination reaction H + O₂ (+M) → HO₂ (+M) between 300 and 900 K, 1.5 and 950 bar, and in the bath gases M = He, Ar, and N₂

The recombination reaction H + O₂ (+M) → HO₂ (+M) was studied by laser flash photolysis in a high pressure flow cell, over the temperature range 300–900 K, the pressure range 1.5–950 bar and in the bath gases M = He and N₂. Earlier experiments by Hahn et al. (Phys. Chem. Chem. Phys. 2004, 6, 1997) in the bath gas M = Ar were also extended. The data were analyzed in terms of unimolecular rate theory employing new calculations of relevant molecular parameters. Improved energy transfer parameters for the bath gases M = He, Ar, N₂, and H₂O could thus be obtained and complete falloff curves were constructed. In the case of water, the high pressure rates well connect with pulse radiolysis results obtained in supercritical water by Janik et al. (J. Phys. Chem. A 2007, 111, 79).