RATES OF OH RADICAL REACTIONS .19. KINETIC-STUDY OF THE REACTION OD+DNO3-]D2O+NO3

Rate constants for the reaction of OD radicals with DNO3 have been determined in the temperature range 269-446K by a flash photolysis-resonance absorption technique. OD radicals were generated by photolysis of DNO3 at 222 nm with a KrCl excimer laser and were monitored by time-resolved resonance absorption at 307.6 nm. The rate constant in cm3/(mol s) can be represented by the following Arrhenius expressions: for 263 K < T < 323 K, by k = (3.18 +/- 0.77) x 10(9) exp [(241 +/- 70)/T], and for 323 < T < 446 K, by k = (1.86 +/- 0.11) x 10(10) exp[(- 322 +/- 21)/T]. A modest (approximately 40%) increase of the rate constant was observed in the presence of 107 Torr of SF6 at 296 K. At other temperatures the effect of pressure is within the experimental uncertainty. A two-channel mechanism is consistent with the data, one involving formation of a complex intermediate, and the other, direct hydrogen abstraction.