H+O2→OH+O: Excitation function and absolute reaction cross sections

Keβler, K.; Kleinermanns, K.
July 1992
Journal of Chemical Physics;7/1/1992, Vol. 97 Issue 1, p374
Academic Journal
The reaction H+O2 was investigated using translationally excited H atoms from HI photolysis in the range 227–300 nm. An increase in the reaction probability with increasing collision energy up to 175 kJ/mol followed by a decrease at higher E was observed. Rotational distributions were obtained at 240, 250, 254, 262.5, 270, 280, and 290 nm. Absolute reaction cross sections at different collision energies were measured with a calibration method using HNO3 photolysis as a reference: σR (115.7 kJ/mol)=0.18±0.10 Å2, σR (145.1 kJ/mol) =0.24±0.13 Å2, σR (171.9 kJ/mol)=0.65±0.36 Å2, and σR (179.2 kJ/mol)=0.45 ±0.25 Å2. The experimental values are compared with cross sections from trajectory calculations on an ab initio H+O2 potential energy surface. Good agreement was obtained at low and very high energies while in the intermediate range 145–210 kJ/mol the measured cross sections were considerably higher than the calculated ones. Possible reasons for this discrepancy are discussed.


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