Rate coefficient for the reaction H + O{sub 2} {yields} OH + O: Results from 2000 to 5300 K

Abstract

Tunable-laser flash-absorption has recently provided an unprecedented extension of the temperature range over which the rate of the reaction H + O{sub 2} {yields} OH + O has been measured, resolving an 18-year-old controversy over the high-temperature behavior of the rate of the most important reaction in combustion. Studies have shown that the rate of the above reaction follows a simple Arrhenius expression, k(T) = 1.62 {times} 10{sup {minus}10} exp[{minus}7474/T(K)] cm{sup 3} s{sup {minus}1}, from 960 to 5300 K. Previously, measurements by one group extended only up to 3300 K. At 2600 K, the highest temperature studied by three other groups, the measured rates differed by 220%. To obtain the new results, a shock wave was used to quickly heat a sample and the rate of production of OH directly behind the shock wave was measured by tuning the wavelength of a pulsed dye laser to a region of strong absorption by the OH molecule. The strength of this absorption was measured as a function of distance behind the shock wave by directing the light from the laser beam onto a linear-array detector. This technique is capable of measuring the rates of very fast reactions, and is ideal for precisemore » studies at very high temperatures where the rates of chemical reactions are the fastest.« less