TIME-RESOLVED STUDY OF H + HBR-]BR + H2 AND REANALYSIS OF RATE DATA FOR THE H2 + BR2 REACTION OVER THE TEMPERATURE-RANGE 214-1700-K

The rate coefficient, k1, for the reaction H + HBr --> H2 + Br has been measured by laser flash photolysis of HBr at 193 nm, observing both the rate of disappearance of H and the rate of appearance of Br by resonance fluorescence, over the temperature range 298-546 k1 = 1.87 x 10(-11) exp (-310 K/T) cm3 molecule-1 s-1. Combining the data with other measurements of k1 and of estimates of k-1 from higher temperature photolysis and pyrolysis studies of the H2 + Br2 chain reaction, coupled with the equilibrium constant, K1, gives k1 = 2.1 x 10(-14)(T/K)1.05 exp(-82 K/T) cm3 molecule-1 s-1 over the temperature range 214-1700 K and k-1 = 6.9 x 10(-12)(T/K)0.43 exp(-8970 K/T) cm3 molecule-1 s-1. Finally, combination of the expression for k1 with the inhibition term for the H2 + Br2 chain reaction results in k2 = (1.6 +-/ 0.6) x 10(-10) cm3 molecule-1 s-1 for the reaction H + Br2 --> HBr + H over the temperature range 300-500 K, rising to (5+5-3) x 10(-10) cm3 molecule-1 s-1 at 1700 K.