KINETIC-STUDY OF THE OH+H-2 REACTION FROM 800-K TO 1550-K

Direct measurements of the rate constant for the bimolecular reaction OH + H-2 --> H + H2O have been completed in the temperature range 800-1550 K. In these experiments, small amounts of water vapor were photolyzed with an excimer laser to "instantaneously' create OH radicals and H atoms. The subsequent time history of the OH radicals was monitored by using laser-induced fluorescence. Analysis of the OH removal rate as a function of added hydrogen yielded the rate constant for the above reaction. The temperature range of our measurements bridges the gap between the recent shock tube data (1246-2581 K) of Michael and Sutherland, Frank and Just; Davidson, Chang, and Hanson and the quartz cell flash photolysis data (250-1050 K) of Tully, Ravishankara, and co-workers. Our data are in very good agreement with these previous data sets in the overlap region. By combining our data with these four data sets, we derive a new rate constant expression, k = (3.56 X 10(-16)T1.52 exp[-1736/T] cm3 molecule-1 s-1, that is applicable in the temperature range 250-2581 K.