Rate constant for H+H+Ar = H₂ + Ar from 1300 to 1700 K

Abstract

. AbstractShock tube experiments on the decay of OH-radical concentration after shock-initiated combustion of H2:OZ:Ar = 10:1:89 mixtures were analyzed to give the rate constant 1 X 1015 cm6mol-*s-' for the reaction H + H + Ar = H z + Ar over the temperature range 1300 to 1700 K.

Mechanism of isotope exchange reaction between methane and deuterium

“…This set was augmented by twelve isotope exchange reactions consisting of various deuterium analogs of H + CH 4 = CH 3 + Hz, shown as reactions (8), (9), and (17)- (26) of Table I . The rate constants for each of these assumed exchange reactions were derived from the rate constant measured for reaction (2) by Clark and Dove [6] first by correcting for the effect of the collisional reduced mass upon the collision frequency.…”

“…Perusal of the first three lines of Table 111 shows that neither the stripping nor the complex formation mechanisms and rate constant expressions predict the observed amount of isotope exchange, the complex formation version being substantially less successful than the stripping version. Numerous attempts were made to investigate the sources of the general shortfall in predicted exchange, The conclusion drawn is that the computed amount of exchange is directly proportional to the rate constant of reaction ( I ) , moderately affected by the rate of reaction (8), and only slightly dependent on other rate constants. The isotope exchange experiments are indeed, as expected, rate limited by the rate of formation of chain centers; they are not affected by chain termination under the conditions of the WBLB experiments, for the results were unaffected by changes in the rate constants assumed for CH3 + CHs = C2H6 or the three H and D atom recombination rates.…”

“…Consideration of the relative rates computed in the WBLB simulations showed that the role of the impurity is to provide additional C H I radicals directly and H atoms indirectly. The H atoms feed primarily into reaction (6), the C H I radicals primarily into reaction (-9), both producing increased D atom concentrations that, via reaction (8), produce increased amounts of HD. The exchange without impurity proceeds along these lines also.…”

“…It was found in the computations that the temperature change due to reaction never exceeded 1°K for the residence times of the WBLB experiments. See Mallard and Owen [8].…”

Studies of a model of hydrogen recombination

“…The factor p,q, increases with temperature, which may be the most unrealistic feature of the model. The hard sphere collision cross section o in [14] is treated here as an adjustable parameter. Assuming for it a not unreasonable value of 10 A2, one obtains for hydrogen [16] k,,, = (5.4 x lo8) T-0.315y(0.685,0.136/T) x q,p e2 molT2 s-I For deuterium the factor mA2 Or in the denominator of [14] is twice as large as it is for hydrogen.…”