title: Reaction of O2 with the hydrogen atom in water up to 350 degrees C.
abstract: The reaction of the H* atom with O2, giving the hydroperoxyl HO2* radical, has been investigated in pressurized water up to 350 degrees C using pulse radiolysis and deep-UV transient absorption spectroscopy. The reaction rate behavior is highly non-Arrhenius, with near diffusion-limited behavior at room temperature, increasing to a near constant limiting value of approximately 5 x 10(10) M(-1) s(-1) above 250 degrees C. The high-temperature rate constant is in near-perfect agreement with experimental extrapolations and ab initio calculations of the gas-phase high-pressure limiting rate. As part of the study, reaction of the OH* radical with H2 has been reevaluated at 350 degrees C, giving a rate constant of (6.0 +/- 0.5) x 10(8) M(-1) s(-1). The mechanism of the H* atom reaction with the HO2* radical is also investigated and discussed.
authors.affiliation: Notre Dame Radiation Laboratory, Notre Dame, Indiana 46556, USA.
authors.forename: Ireneusz
authors.initials: I
authors.lastname: Janik
authors.forename: David M
authors.initials: DM
authors.lastname: Bartels
authors.forename: Timothy W
authors.initials: TW
authors.lastname: Marin
authors.forename: Charles D
authors.initials: CD
authors.lastname: Jonah