The
H + O2
+ M → HO2
+ M reaction was investigated at temperatures between 1050 and 1250 K and pressures from 7 to 152
bar behind reflected shock waves in gas mixtures of H2, O2, NO, and bath gases of Ar, N2 and H2O. Narrow
linewidth laser absorption of NO2 at 472.7 nm was used to measure quasi-steady NO2 concentration
plateaus in experiments designed to be sensitive only to the H + O2
+ M → HO2
+ M and the
relatively well-known H + NO2
→ NO + OH and H + O2
→ OH + O reaction rates. The pressure dependence of the reaction was studied
by measuring the fall-off of the reaction for M = Ar over a 10–152 bar pressure range. A simple modified Hindered-Gorin
model of the transition state is used in an RRKM analysis of the results to facilitate comparisons
of this work with measurements from other researchers at lower pressures. The RRKM calculations can also
be described, using the simple functional form suggested by Troe, with the following:
k∞/cm3
molecule−1 s−1
= 4.7 × 10−11 (T/300)0.2; k0(Ar)/cm6 molecule−2 s−1
= 2.0 × 10−32 (T/300)−1.2; k0(N2)/cm6
molecule−2 s−1
= 4.4 × 10−32 (T/300)−1.3; k0(H2O)/cm6 molecule−2 s−1
= 3.4 × 10−31 (T/300)−1.0; Fc
= 0.7 for Ar and N2 and 0.8
for H2O. Measured values of the reaction rate for M = Ar in the highest pressure experiments fall below both
simple RRKM analysis and the more sophisticated treatment of Troe using an ab initio potential energy surface.
Collision efficiencies of N2 and H2O relative to Ar at 1200 K are 3.3
and 20 respectively.
You have access to this article
Please wait while we load your content...
Something went wrong. Try again?